M12 Chapter 12 On Board Diagnostics (OBDII) and Computer Systems
Heated oxygen sensor
A sensor that is electrically heated to accurately sense exhaust gases regardless of operating temperature.
The first of the design features of computerized engine management is to maintain air-fuel ratios as close to _______ to allow optimal catalytic converter operation and improve ________.
14.7:1, fuel economy.
The standard DLC (Figure 12-22) is a _____ connector. The same pins are used for the same information, regardless of the vehicle's make, model, and year. The connector is ________ and has guide keys that allow the scan tool to be installed only one way. Using a standard connector design and designating the pins allows _______ retrieval with any scan tool designed for OBD II. Some European vehicles meet OBD II standards by providing the designated DLC along with their own connector for their own scan tool.
16-pin, D-shaped, data,
Long-term fuel trim (long-term FT)
Moves slowly to keep short-term fuel trim near zero.
All of the system's HO2S sensors are monitored once per _______, but the heated oxygen sensor monitor provides separate tests for the _________ sensors.
drive cycle, up and downstream
For misfire and fuel monitors, if the fault does not occur on three consecutive __________ under similar conditions, the _____ is turned off.
drive cycles, MIL
If the RAM has a volatile memory, new information will be _______ into the RAM when the engine is ________. Many parts of the RAM are nonvolatile, meaning that the information is not _________ when the vehicle is turned off.
written, restarted, erased
Type A and type B engine misfires are detected by the misfire monitor. When detecting a type A misfire, the monitor checks cylinder misfiring over a _________ period. If cylinder misfires are between _______, the monitor considers the misfiring to be excessive.
200 rpm, 2 and 20%,
Programmable read only memory (PROM)
A computer chip containing some of the computer program. This chip is removeable in some computers.
The PCM commands the ______ to open and then checks the pressure at the two _________ connected to the DPFE sensor. With the EGR valve open and EGR flow through the orifice, there should be higher pressure at the _________ to the DPFE sensor (Figure 12-14).
EGR valve, exhaust hoses, EGR valve fitting
Although many vehicles no longer have an _________, the exhaust gas recirculation (EGR) monitors use several different strategies to determine if the system is operating properly. Some systems look at the __________ (MAP) signal, energize the EGR valve, and look for corresponding change in _______ levels.
EGR valve, manifold absolute pressure, vacuum
The microprocessor stores this altered calibration in the__________. The microprocessor now refers to this new calibration during _________; thus, normal engine performance is maintained. If a sensor output is erratic or considerably out of range, the computer may ________ this input.
KAM, calculations, ignore
The computer has a series of monitors that were mandated through OBD II legislation. A monitor watches a particular system for _____ and ______ performance. The monitors in use at this time are discussed in the following paragraphs.
faults, degraded
The components in the microprocessor are etched on an ________ (IC) that is small enough to fit on a _________. The _________ containing the IC is mounted in a flat, rectangular, protective box.
integrated circuit, fingertip, silicon chip
Since 1996, enhanced EVAP system vehicles have an enhanced evaporative system monitor (Figure 12-15). This system detects ________and __________ in the EVAP system.
leaks, restrictions
A catalytic converter stores oxygen during______ engine operation and gives up this stored oxygen during rich operation to burn up excessive ________. Catalytic converter efficiency is measured by monitoring the __________ capacity of the converter during closed-loop operation.
lean, hydrocarbons, oxygen storage
The first character of the code is a _____. This defines the system where the code was set. The U-codes are designated for use as __________ codes.
letter, network problem
When the catalytic converter is storing oxygen properly, the downstream HO2S sensors provide ________ voltage signals. If the catalytic converter is not storing oxygen properly, the voltage signal frequency increases on the _______ HO2S sensors until the frequency of the downstream HO2S sensors approaches the frequency of the ________ HO2S sensors (Figure 12-10).
low-frequency, downstream, upstream
Most OBD II systems allow a random ________ of about 2% before a misfire is flagged as a fault. It is important to note that this monitor looks at only the speed of acceleration of the crankshaft during a cylinder's _________. It cannot determine if the problem is ______,_______, or mechanical-related. Misfire is categorized as type A or type B.
misfire rate, firing stroke, fuel, ignition
The CCM checks signal inputs that do not have their own _______. One of the methods used to check components is a rationality check. During a rationality check, the monitor uses other sensor _______________ to determine if a sensor reading is proper for the present conditions.
monitor, readings and calculations,
All OBD II scan tools include a readiness function showing all of the ____________ on the vehicle and the status of each, complete or incomplete. If vehicle travel time, operating conditions, or other parameters were _________ for a monitoring sequence to complete a test, the scanner will indicate which monitoring sequence is not yet complete (Figure 12-18).
monitoring sequences, insufficient,
The third through fifth characters are ______. These describe the fault. The third character of a powertrain code tells you where the fault ______. The remaining two characters describe the exact _________that set the code. "P1"xxx codes are manufacturer specific.
numbers, occurred, condition
A pending DTC is a code representing a fault that has _______ but not enough times to illuminate the _______. Some _______ are capable of reading pending DTCs with the continuous DTCs.
occurred, MIL, scan testers
Included in the program is information that tells the microprocessor when to _______ input (based on temperature, time, and so on), how to ______ the input, and what to do with it once it has been ________.
retrieve, process, processed
This enhanced system has to be able to detect leaks as small as ______ diameter. To accomplish this, the system uses a fuel tank pressure sensor, a vent solenoid, and a purge solenoid. These three devices allow the PCM to run ___________ checks for leaks in the system. (See Chapter 12 for more details.)
0.020 in, pressure and vacuum
Air from the pump is now delivered to the exhaust manifold. The purpose of the air pump is to oxidize _______ in the exhaust manifolds from __________ seconds after the engine has started and until the _________ is working properly.
HC and CO, 20 to 120, catalytic converter
At certain times, the heated oxygen sensor monitor varies the fuel delivery and checks for __________ response. A ______ response in the sensor voltage signal frequency indicates a __________. The sensor signal is also monitored for excessive voltage.
HO2S sensor, slow, faulty sensor
Enable criteria
Conditions that must be met before the PCM can initiate a test of a component or system. These criteria are specific to the sensor or system being tested.
An example of this would be an ECT sensor that suddenly goes from a warm engine reading to a cold engine reading, after the engine has been running for several minutes. The CCM checks these inputs:
Crankshaft position sensor Output shaft speed sensor Ignition diagnostic monitor Camshaft position sensor Vehicle speed sensor
In recent years, the AIR system is being replaced by functions of ______ such as injecting _____ during the __________ while cold, and by the VVT system varying valve timing events when cold.
DFI, fuel, compression stroke,
The central processing unit (CPU) is the ___________of a computer. The CPU is constructed of thousands of ________ that are placed on a small chip. The CPU brings information into and out of the computer's ______.
brain, transistors, memory.
The microprocessor is the _______________ chip in a computer.
calculating and decision-making,
The microprocessor may write the results of ______ and other changeable data into the RAM. The microprocessor can ____,____,_____ RAM information.
calculations, write, read, and erase
Mode 9 (if supported) allows the PCM to identify: The vehicle's identification number (VIN) The PCM's _________ and _________
calibration ID, calibration verification
On many V-type engines, there are two primary or upstream HO2S sensors, one for each ________. These individual sensors report the _________ and _________ for the cylinders on that side of the engine.
cylinder bank, air-fuel mixture, combustion
If a cylinder misfires, unburned hydrocarbons (HCs) are exhausted from the ________, and these excessive HC emissions enter the ___________. When the catalytic converter changes these excessive HC emissions to carbon dioxide and water, the catalytic converter is overheated and the _______ in the converter may melt together into a solid mass. If this occurs, the converter is no longer efficient in reducing ______.
cylinder, catalytic converter, honeycomb, emissions.
Once the HO2S is warm enough to produce a ________, the voltage should be low if the AIR pump is delivering air to the __________. The secondary AIR monitor will indicate a _______ if the HO2S voltage is low at this time.
voltage signal, exhaust manifold, pass
Input. A __________ sent from an input device. The device can be a __________ activated by the driver, technician, or mechanical part.
voltage signal, sensor or button
The information stored in the ______ is subject to change. Since the sensor input information changes frequently in relation to various operating ________, this information is stored in the RAM (Figure 12-4).
RAM, conditions,
During the chip manufacturing process, information is programmed into the _____. This information is not erased even if the ___________ are disconnected.
ROM, battery terminals
Information retrieval
Refers to the microprocessor retrieving information from some of the computer memories.
Information storage
Refers to the microprocessor sending information to some of the memories where it is stored for future reference.
This allows the technician to look at the action of _________ when the code was set and can help identify the cause of the problem. Only one __________ is available.
Sensors and actuators, freeze frame
The connector pins are arranged in two rows and are numbered consecutively. ______ of the sixteen pins have been assigned by the _______ standard. The remaining nine pins can be used by the individual __________ to meet their needs and desires.
Seven, OBD II, manufacturers
Failure record
Some manufacturers such as GM have provided more than one freeze frame known as "failure records." See freeze frame.
Trip
Starting and driving the vehicle until five monitors are completed.
Snapshot
A feature of OBD II systems that captures all data present when the computer detects a problem and sets a trouble code.
Type A misfire
A misfire that can cause immediate catalyst damage.
Type B misfire
A misfire that results in one and one half times the emission output standard.
Parameter identification (PID)
A mode that allows access to certain data.
Catalyst efficiency monitor
A monitor in OBD II systems that checks the oxygen content of the exhaust before it enters the catalytic converter and after it leaves the converter.
Short-term fuel trim (short-term FT)
adds or subtracts fuel to correct for small or temporary changes.
The heated oxygen sensor monitor will command the PCM to vary the _________ to check the rear _______ response.
air-fuel ratio, HO2S sensor
If the malfunction corrects itself, the ______ is turned off after three consecutive __________ in which the fault is not present.
MIL, drive cycles
To detect a type B cylinder misfire, the misfire monitor checks cylinder misfiring over a _______ period. A type B misfire occurs if cylinder misfiring exceeds _______ during this 1,000 rpm period. This amount of cylinder misfiring may not overheat the catalytic converter, but it may cause excessive ________.
1,000 rpm, 2 to 3%, emission levels
Most DTCs are automatically erased after _______ warm-up cycles if the fault is not detected during that time. Some manufacturers retain erased DTCs in a __________ condition. This can be useful if the technician notices a pattern of component failure, all of which may be related to a single intermittent cause like _________.
40, flagged, low fuel pressure.
There are two main types of OBD II diagnostic trouble codes (DTCs), type _______. There are also type C and type D codes that are not emissions related. The type C codes can illuminate a _______ other than the MIL on some models; type D codes do not usually illuminate any lamp but can be used by the technician to aid _________.
A and B, lamp, troubleshooting
Electronically erasable programmable read only memory (EEPROM)
A computer chip that may be easily erased and reprogrammed with special equipment.
Random access memory (RAM)
A computer chip that the microprocessor can write information into and retrieve information from.
Fuel system monitor
A monitor that checks short- and long-term fuel corrections during closed loop.
Calibration
A set of instructions programmed into the PCM or contained on a PROM that tailors the PCM to the vehicle.
Drive cycle
A specified set of driving conditions. The drive cycle is important to adaptive strategies of a computer. The proper drive cycle is also required of OBD II systems to complete monitor tests on certain systems.
Flashing
A term that is used to describe programming an OBD II PCM.
Reflashing
A term used to describe the reprogramming of a PCM, usually to correct a problem repaired by updated software.
The passive test also looks for a higher HO2S voltage when the _______ flow to the exhaust manifold is turned off by the ________. When the AIR system passes the passive test, no further _______ is done. If the AIR system fails the passive test or if the test is inconclusive, the ___________ in the PCM proceeds with the active test.
AIR, PCM, testing, AIR monitor
The definition of a trip depends on the monitor involved. For instance, the fuel system monitor will run once the following criteria are met:
Closed loop Coolant temperature between 20 and 257 degrees Fahrenheit Intake air temperature between 20 and Mass airflow between 1 and 500 grams per second Barometric pressure greater than 10.7 psi Engine speed between 400 rpm and 5,700 rpm Vehicle speed less than 80 mph (129 km/h) Manifold absolute pressure between 2.2 and 12.3 psi
The PCM checks the EGR flow by checking the ____________ against an expected DPFE value for the engine operating conditions at steady throttle within a specific rpm range. If a fault is detected in any of the EGR monitor tests, a DTC is set in the ________. If the fault occurs during two consecutive ___________, the MIL is illuminated. The EGR monitor operates once per OBD II trip.
DPFE signal value, PCM memory, drive cycles,
Mode 3 permits scan tools to obtain stored _______. The information is transmitted from the __________ to the scan tool following an OBD II mode 3 request. Either the DTC or its _______, or both will be displayed on the scan tool.
DTCs, PCM, descriptive text
OBD II computers are equipped with an electronically erasable programmable read only memory (EEPROM). This type of memory chip can be reprogrammed via a _________ pass through programming device.
J2534
The microprocessor can read and write information to and from the KAM and it can erase _________ information (Figure 12-6). However, the KAM retains information when the ignition switch is turned _____. When the ________ is disconnected from the computer, the KAM memory is erased. The KAM is used for adaptive strategies that are explained in the next section.
KAM, off, battery power,
The EGR systems from Ford may contain a delta pressure feedback EGR (DPFE) sensor. The latest DPFE design subtracts the _________ from that of the pressure measured at the _______ to determine _______.
MAP pressure, EGR valve, EGR flow.
With the engine idling and the EGR valve closed, the PCM checks for EGR flow again by comparing ______ to the pressure at the ___________. When the EGR valve is closed and there is no EGR flow, the _______ should be the same at both areas. If the pressure is different at these two hoses, the EGR valve is ________.
MAP, EGR valve fitting, pressure, stuck open.
For the catalyst efficiency, H20S, EGR, and comprehensive component monitors, the ________ is turned off if the same fault does not reappear for three consecutive ________. When the fault is no longer present and the MIL is turned off, the DTC is erased after _________ engine warm-up cycles. A technician may use a __________ to erase DTCs immediately.
MIL, drive cycles, 40, scan tester
The input signals monitored in this way are illustrated in Figure 12-17:
Mass airflow sensor Manual lever position sensor Throttle position sensor Accelerator pedal position sensor Engine coolant temperature sensor Intake air temperature sensor Knock sensors System wiring
The system also monitors lean-to-rich and rich-to-lean time responses. This test can pick up a lazy ______ that cannot switch fast enough to keep proper control of the _____ in the system. These sensors are the heated type, and the amount of time before activity of the sensor signal is present is an indication of whether it is functional or not. Some systems use _________ to indicate if the heater is working or not.
O2 sensor, air-fuel mixture, current flow
OBD II systems provide an outstanding opportunity to simultaneously perform multiple tests on engine systems. The root cause of most drivability problems can likely be observed in the __________. It is the interrelationship of the data that will reveal a potential problem area. For example, consider what occurs during a snap acceleration test. The TPS ________ quickly rises, the MAF also rises as a result of an increased volume of ______, and the _______ will increase along with the _____ from the oxygen sensor, indicating a rich condition.
OBD II data, voltage, intake air, rpm, voltage
Comprehensive component monitor (CCM)
One of the monitor systems in an OBD II system that checks the activity and efficiency of several systems and major components.
Generic codes begin with _____; manufacturer-specific codes begin with a ____. P2XXX codes are ____________ codes, ____XXX can be either manufacturer specific or generic.
P0, P1, generic, P3
When the engine is started, the ________ signals the relay to start the _________. This module supplies the _________ required for air pump operation. The air pump may provide a ________ delay in pump operation after the engine is started.
PCM, air pump, high current, 10-second
The _________ monitors the crankshaft acceleration time for each cylinder firing. If a cylinder is contributing normal power, a specific crankshaft acceleration time occurs. When a cylinder misfires, the cylinder does not contribute to _________, and crankshaft acceleration for that cylinder is ______.
PCM, engine power, slowed.
VMode 10 Permanent Codes. Mode 10 was added a few years ago. The name is a bit misleading, as the codes are not really permanent, but they can only be erased by the ________. The intent is to keep a repair technician from clearing a ______ and then only driving the vehicle far enough to get the readiness code to _______. These codes cannot be cleared by using a scan tool or disconnecting the battery.
PCM/ECM, code, reset
The PCV system monitor was phased in starting in 2002 and required for vehicles built after the 2004 model year. This monitor has the ability to monitor__________ for disconnection. GM has built their PCV into the ________ manifold. Since this eliminated the hoses, it also eliminated the need for a separate system.
PCV hoses, intake
The elimination of the replaceable PROM chip was part of the OBD II legislation to prevent the use of aftermarket high-performance _________. There is an advantage to not using the replaceable PROM in that many updates for engine performance concerns can be performed during service by changing the ________ of the PCM without the need for having ___________ parts. This calibration change is called reflashing the PCM.
PROMs., calibration, replacement
Adaptive strategy
The ability of a computer to adapt to certain defects in the system.
Microprocessor
The decision-making chip in a computer.
Keep alive memory (KAM)
The microprocessor can read information from the KAM but it cannot write information into this chip. KAM memory is retained when the ignition switch is turned off, but it is erased when battery power is disconnected from the computer.
Read only memory (ROM)
The microprocessor can read information from the ROM chip but it cannot write information into this chip.
Monitored outputs include the following:
Wide-open throttle A/C cutoff Shift solenoid 1 Shift solenoid 2 Torque converter clutch solenoid HO2S (A/F sensor) heaters High fan control Fan control Electronic pressure control solenoid Fuel pump module Throttle actuator control (if equipped) Variable valve timing
The memories store information regarding the ideal _________ for various operating conditions. The sensors inform the computer about the ________________ operating conditions.
air-fuel ratios, engine and vehicle
The PCM also energizes the _________bypass solenoid. When this solenoid is energized, it supplies vacuum to the ___________ valves. This action opens the normally ______ air diverter valves.
air-injection, dual air diverter, closed
Currently, there are three possible first character codes: B for _____, C for _______, and P for _________
body, chassis, powertrain.
A program is a group of ________ that is followed by the microprocessor. The program guides the microprocessor in _________.
instructions, decision making.
Type A misfire could cause immediate ______ damage. Type B misfire could cause _______ of 1.5 times the design standard and could cause an inspection/maintenance (I/M) failure. When there is a type A misfire, the MIL will _____. If there is a type B misfire, the MIL will turn on but will not _____.
catalyst, emissions, flash
The oxygen sensor behind the __________ is often called the ________ O2 sensor.
catalytic converter, downstream
Most adaptive strategies have two parts: short-term fuel trim (STFT) and long-term fuel trim (LTFT). Short-term strategies are those immediately enacted by the computer to overcome a __________ in operation. These changes are _________. Long-term strategies are based on the ______ about the short-term strategies. These changes are more ________. To understand how a computer adapts itself to certain conditions, you must understand the differences between short-term fuel trim (adaptive) memory and long-term fuel trim (adaptive) memory.
change, temporary, feedback, permanent
The fuel system monitor checks short-term FT and long-term FT while the PCM is operating in ________. Fuel trim is a feedback system that looks at the present state of this _______ compared to the ______ range.
closed loop, oxygen sensor, desired
During the active test, the PCM cycles the AIR flow to the exhaust manifold on and off during __________ operation and monitors the _______ HO2S voltage and the _______ FT value.
closed-loop, pre-catalyst, short-term
Some manufacturers turned to secondary air injection (AIR) to reduce _____________. Cold start emissions make up a large share of the vehicle emissions, because they occur before the ________ is hot enough to reduce emissions, and the __________ sensor is hot enough to accurately report emissions.
cold start emissions, converter, oxygen or A/F
A misfire means a lack of _______ in at least one cylinder for at least one combustion event. A misfire pumps unburned _____ through the exhaust. Although the converter can handle an occasional sample of raw fuel, too much fuel to the converter can ______ and destroy it. A type A misfire sets a trouble code on the ________.
combustion, fuels, overheat, first failure.
The basic advantage of the freeze-frame feature is the ability to look at the existing ___________ when a code was set. The freeze frame is set automatically by the _______. This will be especially valuable for diagnosing ____________ problems. Whenever a code is set, a record of all _______ activities will be stored in memory.
conditions, PCM, intermittent, related
Output. After the computer has processed the sensor input and checked its programmed instructions, it will put out ________________ to various output devices. These output devices may be instrument panel displays or __________. The output of one computer may also be an _________ to another computer.
control commands, output actuators, input
Mode 8 is the request for _______ of an onboard system test or component. In this mode, the technician can use the scan tool to control the ________ to test a system and its related components. Presently, mode 8 is most commonly used for testing the _______ system. The EVAP leak test is conducted in this mode because the _______ has set conditions to enable the technician to test the EVAP system for leaks.
control, PCM, EVAP, PCM
The catalyst efficiency monitor is still measuring the efficiency of the __________ using the post-converter HO2S sensor regardless of whether a HO2S sensor or A/F sensor is used in the _________
converter, pre-catalyst location.
When stored information is requested from a specific address, the memory sends a ________ of this information to the microprocessor. However, the _______ stored information is still retained in the ________
copy, original, memory address.
Cylinder misfire monitoring
crankshaft speed acceleration as each cylinder fires.
Cylinder misfire monitoring uses a complex strategy to calculate __________ acceleration as each cylinder fires. If a misfire occurs, the relative speed of the crankshaft momentarily __________ and resumes when the next ________ fires.
crankshaft speed, slows, cylinder
Cylinder misfire monitoring requires measuring the contribution of each ________ to ______. The misfire monitoring system uses a highly accurate crankshaft angle measurement to measure the _________ each time a cylinder fires. A high data rate crankshaft sensor is required for this function (Figure 12-12).
cylinder, engine power, crankshaft acceleration,
One type of failure is an exception to this rule—misfire. Fuel system misfires will overwrite any other type of _______ except for other ________ misfire data. This data can be removed only with a scan tool. When a scan tool is used to erase a DTC, it automatically erases all _______________ associated with the events that lead to that DTC.
data, fuel system, freeze-frame data
Snapshot refers to a short "movie" of several frames of _______ that can be triggered by the technician with a ________.
data, scan tool.
When a computer has adaptive strategy, a short learning period is necessary: After the battery has been ________ When a computer system component has been _________ On a new vehicle
disconnected, replaced or disconnected
The DLC must be easily accessible while sitting in the ______ seat (Figure 12-23). All DLCs must be located somewhere between the ______ of the instrument panel and the _______ of the vehicle. The connector cannot be located on the center console or in a cupholder on the console.
driver's, left end, centerline,
The comprehensive component monitor (CCM) uses two strategies to monitor inputs and two strategies to monitor outputs. One strategy for monitoring inputs involves checking certain inputs for _________ and ___________ values by checking the input signals at the analog-to-digital converter.
electrical defects, out-of-range,
The EEPROM stores data without the need for a continuing source of ___________. If the ECM is replaced, then it will have to be ________. Sometimes additional components may have to be relearned, such as the _________ (CKP) sensor and the __________ system.
electrical power, reprogrammed, crankshaft position, anti-theft
A heated oxygen sensor is __________ heated to accurately sense ________ regardless of operating temperature.
electrically, exhaust gases
The second of the design features of computerized engine management is to Accurately control critical ___________ devices such as EGR and carbon canister/evaporative control system.
emission control
Mode 2 is the freeze-frame data access mode. This mode permits access to ______-related data values from specific generic PIDs. These values represent the operating conditions at the time the ________ was recognized and logged into memory as a ________.
emission, fault, DTC
The codes are well defined and can lead a technician to the problem. A scan tool must be used to access and interpret __________ regardless of the make and model of the vehicle (Figure 12-24).
emission-related DTCs
Processing. The computer uses the input information and compares it to programmed ___________. This information is processed by ___________ in the computer.
instructions, logic circuits
The PCM reset mode, mode 4, allows the scan tool to clear all __________ diagnostic information from its memory. Once the PCM has been reset, the PCM stores an inspection maintenance readiness code until all OBD II system monitors or components have been tested to satisfy an __________ without any other faults occurring. Specific conditions must be met before the requirements for a trip are satisfied.
emission-related, OBD trip cycle
Once a DTC and a set of freeze-frame data are stored in memory, they will stay in memory even if other ____________ DTCs are stored. The number of these sets of freeze frames that can be stored are _______.
emission-related, limited.
An OBD II system continuously monitors the entire _______ system, switches on an _____ if something goes wrong, and stores a fault code in the ________ when it detects a problem.
emissions, MIL, PCM
The FTP is an established testing program used by the government to certify new vehicles as compliant with _________ regulations. When a component or strategy failure allows emissions to exceed this FTP level, the ______ is illuminated to inform the driver of a problem, and a __________ is stored in the PCM.
emissions, MIL, diagnostic trouble code
The system looks at any electronic input that could affect _______. The strategy is to look for opens and shorts or ___________ that are out of the normal range. It also looks to see if the ________ have their intended effect on the system and to monitor other abnormalities.
emissions, input signal values, actuators
The second way the system defines similar conditions is _______ within ______ compared to when the fault was detected.
engine load, 10%
All systems require multiple input signals to indicate _________,__________, and engine ___________ used to determine fuel and spark requirements. The vehicle's computer is programmed to execute specific commands based on the input data.
engine load, speed, temperatures
The first way the system defines similar conditions is _________ within _________ compared to when the fault was detected.
engine speed, 375 rpm,
The misfire monitoring sequence includes an adaptive feature compensating for variations in engine characteristics caused by manufacturing tolerances and component wear (Figure 12-13). It also has the adaptive capability to allow vibration at different __________. When an individual cylinder's contribution to engine speed falls below a certain threshold, the misfire monitoring sequence calculates the ________,_________,and load factors before setting a misfire code.
engine speeds and loads, vibration, tolerance
An OBD II drive cycle (Figure 12-20) consists of an ________ and vehicle operation that brings the vehicle into ________ and includes whatever specific operating conditions are necessary either to initiate and complete a specific monitoring sequence or to verify a symptom or a repair. A monitoring sequence is an operational strategy designed to test the operation of a specific system, function, or component.
engine start, closed loop,
The third way the system defines similar conditions is ________ state or coolant ________ must match the temperature when the fault was detected.
engine warm-up, temperature
A newly designed fuel tank filler cap is used on this system. In these enhanced systems, an _________ leak or a missing __________will cause the MIL to turn on.
evaporative system, fuel tank cap
If a computer has adaptive strategy capabilities, the computer can actually learn from past _________. For example, the normal voltage input range from a __________ (TPS) may be 0.6 volt to 4.5 volts. If a worn TPS sends a ______ signal to the computer, the microprocessor interprets this signal as an indication of component wear.
experience, throttle position sensor, 0.3-volt
Some manufacturers such as GM have provided more than one freeze frame known as _________ . An example is shown in Figure 12-26. A freeze frame should not be confused with a _______. Most scan tools are capable of a snapshot, which is triggered by a technician. The snapshot is a series of frames of data (movie) taken during a __________ problem that can be analyzed in the shop.
failure records, snapshot, drivability
A type A DTC will illuminate the MIL on the first _______. Type B codes are "_______" on the first failure, and a MIL is illuminated on the second consecutive failure unless the pending DTC is for ___________.
failure, pending, fuel trim or misfire
These information storage locations may be compared to ________ in a filing cabinet, and each location contains one piece of __________.
file folders, information.
If the misfire monitor detects a type A cylinder misfire and the PCM doesn't shut off the injector or injectors, the MIL light begins ______. When the misfire monitor detects a type A cylinder misfire and the PCM shuts off the __________, the MIL is illuminated ________.
flashing, injector or injectors, continually.
When the downstream HO2S voltage signals reach a certain ___________, a DTC is set in the PCM _________. If the fault occurs on three ________, the MIL light is illuminated. The placement of the HO2S sensors' sensors are shown in Figure 12-11.
frequency, memory, drive cycles
A new fuel cap that was easier to install was added to prevent setting a code from a loose _________. Some vehicles can also illuminate a "check fuel cap" if the cap is loose. Additionally, since 1998, vehicles have to capture _________ in a system called onboard refueling vapor recovery (ORVR). The ORVR is not monitored by OBD II.
fuel cap, refueling vapors
The ________ monitor operates continually when the PCM is in _______. Like the misfire monitor, the fuel system monitor can illuminate the ________ on a second nonconsecutive failure under similar conditions.
fuel system, closed loop, MIL
Under this condition, the PCM may shut off the _______ to the misfiring cylinder or cylinders to limit ________ heat. The PCM may turn off two _____ at the same time on misfiring cylinders. When the engine is operating under heavy load, the PCM will not ______ the injectors on misfiring cylinders.
fuel, catalytic converter, injectors, turn off
Test modes are available only in "__________." All OBD II systems have the same basic test modes. These test modes must be accessible with an OBD II scan tool.
generic mode
OBD vehicles use at least two _______ oxygen sensors, or an ________and an _____ sensor. If the A/F sensor is used, it is in the pre-catalyst position.
heated, oxygen sensor, A/F
The third of the design features of computerized engine management is to Precisely control _________ under all driving conditions adjusted for ___________.
ignition timing, climate and fuel grade.
The term "random access" indicates that the microprocessor can retrieve ___________ from any _________ in any order.
information, RAM address
RAMs may also be designed with a nonvolatile memory. This type of RAM retains ___________ when the ignition switch is turned _____. Some types of nonvolatile RAM can even retain memory when the ___________ is disconnected.
information, off, battery power
While the engine is running, the computer receives a large quantity of __________ from a number of sensors. The computer may not be able to process all this information immediately. In some instances, the computer may receive ___________ that the computer requires to make a number of decisions. In these cases, the microprocessor writes information into memory by specifying a _________ and sending information to this address (Figure 12-3).
information, sensor inputs, memory address
Instead of a fixed, unalterable programmable read only memory (PROM), the PCMs are equipped with an electronically erasable programmable read only memory (EEPROM) to store a large amount of __________. The EEPROM is ____________ into the PCM and is not ________.
information, soldered, replaceable.
The ________ information is processed in the CPU and checked against the program in the computer's ________. The CPU also checks the memory for any other information regarding programmed __________.
input, memory, parameters.
Mode 1 is the parameter identification (PID) mode. It allows access to certain data values, analog and digital _________, calculated values, and system status information. Some of the PID values will be ________, while others are common to all vehicles.
inputs and outputs, manufacturer specific
The PCM faces the _________ (IAT) sensor when the vehicle is started and decides how long it should take for the ________ to reach normal operating temperature. If it does not reach this temperature, the PCM will set a ______ on the second consecutive occurrence (type B code).
intake air temperature, coolant, code
The fourth of the design features of computerized engine management is to Provide more efficient cold engine operation with __________and_________.
lower emissions, faster warm-ups.
The OBD II systems must illuminate the __________(MIL) (Figure 12-7) if the vehicle conditions would allow emissions to exceed ______ times the allowable standard for that model year based on a Federal Test Procedure (FTP).
malfunction indicator lamp, 1.5
The ROM contains look up tables that contain information about how a vehicle should perform. For example, the lookup table would contain the ideal ___________ under various engine operating conditions. The microprocessor compares the _________ to the ideal vacuum in this table. If the sensor inputs indicate that the actual manifold vacuum is different from the ideal vacuum in lookup tables, the microprocessor will take some appropriate action.
manifold vacuum, sensor inputs,
Many of the trouble codes from an OBD II system will mean the same thing regardless of ________. These are the generic codes. However, some of the codes will pertain only to a particular system or will mean something different with each system, they are the manufacturer-specific codes. The DTC is a ______-character code with both _________ (Figure 12-25). This is called the alphanumeric system.
manufacturer, five, letters and numbers
If a generic scan tool is used, the ____________ codes cannot be read. Manufacturer-specific codes can be read only on an "________" scan tool. "P0"xxx codes are mandated.
manufacturer-specific, enhanced
The microprocessor is supported by various _________ that store information and help the microprocessor in making _______. These memory chips are similar in appearance to the microprocessor chip.
memory chips, decisions
Short-term changes are not saved in the computer's _______. All changes to the fuel system happen immediately and occur in direct response to the___________ and/ or other sensors. These changes are also designed to keep the fuel mixture at the ideal stoichiometric ratio of __________
memory, O2 sensor/AF sensor, 14.7:1.
An address is assigned to each ________ location. This address may be compared to the lettering or numbering arrangement on file folders. Each address is written in a _________, and these codes are numbered sequentially beginning with ____.
memory, binary code, 0.
Storage. The program instructions are stored in the computer's _______. Some of the input signals are also stored in memory for _________ later.
memory, processing
Long-term changes are saved in the computer's ________. These stored values are used the next time the engine is operated in a similar __________.
memory, situation and conditions
Metal connecting pins extend from each side of the _________ container. These pins connect the microprocessor to the ___________ in the computer.
microprocessor, circuit board
The second character is a ________. This defines the code as being a mandated code or a special manufacturer code. This number will be a 0, 1, 2, or 3. A 0 code means that the fault is defined or mandated by OBD II. A ______ means that the code is manufacturer specific. Codes with _____ are generic codes, and _____ can be either generic or manufacturer specific.
number, 1 code, P2, P3
Just as with the heated oxygen sensors, the A/F ratio sensors are also monitored by the PCM for performance, lack of activity, ________,_________,_______ in the wiring to them from the PCM.
opens, grounds, or shorts
If an OBD II computer is replaced, the ___________ instructions for the vehicle must be programmed into the computer before use. The replacement PCM is much like a new personal computer that has to have ________ installed before use. Information stored in the PCM has to be tailored to the exact vehicle being serviced according to the _________. This programming is called flashing the PCM
operating, software, VIN.
OBD II standards define a warm-up cycle as a period of vehicle ___________, after the engine had been turned off, in which the coolant rises by at least ______ degrees Fahrenheit and reaches at least ______ degrees Fahrenheit.
operation, 40, 160
The two oxygen sensors are both heated to bring them into _________ sooner, but the heater is not turned on until some warming of the ______ after a cold start. The internal heater is not turned on until the engine coolant temperature (ECT) sensor signal indicates a _______ engine. This action prevents ________ of the ceramic. Gold-plated pins and sockets are used in the HO2S to help prevent corrosion.
operation, exhaust, warmed-up, cracking
If the converter is operating properly, the signal from the pre-catalyst O2 will have _______, while the post-catalyst O2 will be relatively ______ (Figure 12-10). Once the signal from the rear sensor approaches that of the front sensor, the _____ comes on and a ____ is set.
oscillations, flat, MIL, DTC
Mode 5 is the oxygen sensor monitoring test. This mode gives the _________ fault limits and the actual oxygen sensor outputs during the test cycle. The test cycle includes specific operating ______ that must be met to complete the test. This information helps determine the effectiveness of the __________. It is important to note that some A/F sensors report in mode 6.
oxygen sensor, conditions, catalytic converter,
Even though the A/F ratio sensor does not toggle as the _______ does, the computer still knows what the _______ of the post-catalyst should be according to current conditions in the ________, and can make the determination of the catalyst health.
oxygen sensor, frequency, exhaust,
Note that regarding the sensors on V-type engines, bank 1 sensor 1 is the ________ (or A/F sensor) on the side that has the number 1 cylinder. Bank 2 sensor 1 is the oxygen sensor on the ________ bank as number 1. The second sensor on the number 1 side would be bank 1 sensor 2, and so forth.
oxygen sensor, opposite,
The catalyst efficiency monitor uses two _______ (pre- and post-converter) to determine how well the catalytic converter is treating incoming __________. This is accomplished by comparing the ______-catalyst O2 sensor voltages.
oxygen sensors, exhaust gas, pre and post
Long-term changes are triggered to keep all short-term strategies within particular_________. These strategies are not based on the activity of the O2 sensor; rather, they are based on the _______ of the O2 sensor.
parameters, results
Mode 6 is the onboard test of noncontinuously monitored systems. The PCM will indicate the _______ status of each monitored system in one trip. Using this mode, the technician can determine that the monitor has run and passed or failed without having the system fail twice and set the ________. The technician can also tell how closely the monitor passed or failed. The mode can be helpful, but the material has to be decoded from the ________ system. There is more on mode 6 in the Shop Manual. The systems that are monitored include the following:
pass/fail, MIL, hexadecimal,
OBD II and the Society of Automotive Engineers (SAE) standards require the DLC to be mounted in the ________ compartment out of sight of vehicle passengers. The DLC must be a ________connector with ________ defined by the SAE (Figure 12-21).
passenger, 16-terminal, 9 terminals
When a type B misfire is detected, a ________ is set in the PCM memory. A type B misfire can illuminate the MIL on the second __________________ if conditions are similar to the first.
pending DTC, nonconsecutive failure
Most electronically controlled EGR systems use a _________ sensor to determine the actual position of the ________ compared to the commanded value from the ______.
pintle position, EGR valve, PCM.
The thermostat monitor was added in 2002, after the initial OBD II legislation. Since vehicles cause more ______ when cold, not to mention the fact that the vehicle may not get hot enough to boil off _____________ from the oil in the crankcase, A timer is set when the engine is started after a period of sitting to ________.
pollution, unburned fuel and water, cool down
The HO2S are identified by their _______ in relation to the number 1 cylinder and their location relative to the ________. Sensors on the same side of the vehicle as the number 1 cylinder have a _________, and sensors mounted downstream from the converter have a _______ (Figure 12-9).
position, converters, 1 prefix, 2 suffix
The EEPROM is an integrated circuit that contains the program used by the PCM to provide __________. It is possible to erase and reprogram the EEPROM without removing this _____ from the computer. When a modification to the PCM operating strategy is required, it is no longer necessary to replace the __________. The EEPROM may be reprogrammed through the data link connector (DLC) using information from the manufacturer's website.
powertrain control, chip, PCM,
Vehicles that use an A/F sensor instead of an HO2S will use the A/F sensor in the ____________ and still use the HO2S in the ___________
pre-catalyst position, post-catalyst position.
Remember that an oxygen or A/F sensor only "sees" oxygen, the raw fuel (HC) is not detected by the O2 or A/F sensor. What it can react to is the _________ of the oxygen, which can be interpreted as a ________ condition, and actually add more fuel. To prevent this from happening, most late-model vehicles will go into ________ and ignore the oxygen sensor signal during an engine miss, to help protect the ______.
presence, lean, open loop, converter.
The information obtained by the CPU can be altered according to the instructions of the _______. The CPU may be ordered to make _______ decisions on the information received. Once these decisions or calculations are made, the CPU sends out commands to make the required ____________ to the system being controlled (Figure 12-2).
program, logic, corrections or adjustments
Computers with electronically erasable programmable read only memory (EEPROM) have a memory chip that is easily ___________.
programmable.
Flashing the PCM is the initial __________ of a new PCM.
programming,
As the microprocessor performs calculations and makes decisions, it works with the memories in the following ways: The microprocessor can _____________ from the memories. The microprocessor can write_________ into the memories.
read information, new information
The microprocessor can read information from the ___________ (ROM), but information cannot be _______ into the ROM by the microprocessor, and the microprocessor cannot erase ________ information (Figure 12-5).
read only memory, written, ROM
The microprocessor works with memory in two ways: it can _____ information from memory or change information in memory by ______ or ______ new information.
read, writing in, storing
For example, the program may inform the microprocessor when sensor information should be ______ and then tells the microprocessor how to _______ this information. Finally, the program will guide the microprocessor regarding the activation of output control devices such as ___________.
retrieved, process, relays and solenoids.
Some manufacturers use the ABS wheel speed sensors to detect _________ and use this information to modify the _______ sensitivity.
rough roads, misfire code
Ford's strategy for the monitor was to make the hoses large enough that the vehicle wouldn't ______ with the PCV hoses disconnected. The exception is some of Eco-Boost engines. These systems are using a fresh ______ equipped with a pressure sensor to monitor the PCV system for malfunctions, such as disconnected hoses in the system. If the fresh air hose became disconnected, the vehicle would discharge ___________ into the atmosphere.
run, air inlet hose, blow by gases
The fuel trim and misfire codes can be set on a _________ nonconsecutive failure. Additionally, the catalyst monitor must fail three consecutive tests before illuminating the ______. If the MIL _______, a type A misfire is indicated. A flashing MIL means that the catalytic converter could be damaged due to ________ being burned inside the converter.
second, MIL, flashes, raw fuel
The PCM monitors the relay and the air pump to determine if _________ is present. This PCM monitor for the air pump system functions once per ________. When a malfunction occurs in the air pump system on two consecutive drive cycles, a _______ is stored and the ______ is turned on.
secondary air, drive cycle, DTC, MIL
The microprocessor reads the ideal air-fuel ratio information from memory and compares this information with the __________. After this comparison, the microprocessor makes the necessary decision and operates the injectors to provide the exact __________ required by the engine.
sensor inputs, air-fuel ratio
The heated oxygen sensor monitor also checks the frequency of the rear HO2S ___________ and checks these sensor signals for excessively high _______. If the monitor does not detect signal voltage frequency within a specific range, the rear HO2S sensors are considered _____.
sensor signals, voltage, faulty
If enrichment occurs, the injectors respond to the PCM's command based on the other __________. This is a very direct, albeit basic, test that confirms the fundamental operation of the ______. With additional experience, a technician can superimpose other interrelated data to help with even the most complex diagnosis.
sensors' inputs, PCM,
A typical electronic control system is made up of _________,________, and related wiring that is tied into a central processor called a microprocessor or a microcomputer (a smaller version of a ______).
sensors, actuators, computer
For this reason, most computers are designed to_______ a misfiring cylinder's fuel injector. The injector will stay off until the next ________ even if the miss no longer occurs. Additionally, a misfiring cylinder may not only put ______ into the exhaust stream, it also allows ________from the cylinder to enter the exhaust stream.
shut down, key cycle, raw fuel, air
Some Ford vehicles have an electric air pump system controlled by a _________. The relay is operated by a signal from the ______. An air-injection bypass solenoid is also operated by the PCM. This solenoid supplies ________ to dual air diverter valves (Figure 12-16).
solid-state relay, PCM, vacuum,
The PROM contains specific programs such as the __________program, which is designed for the specific requirements of each vehicle. For example, this spark advance program varies with different __________________.
spark advance, transmissions or rear axle ratios.
The DLC cannot be located any lower than the bottom of the __________ and should be visible to a crouched technician entering the vehicle from the driver's side of the vehicle. The DLC cannot be hidden behind ________and must be accessible without tools. Any generic scan tool can be connected to the ______ and can access the diagnostic data stream.
steering wheel, panels, DLC
A RAM with a volatile memory erases ______ information when the ignition switch is _________.
stored, turned off.
A computer is an electronic device that ___________ data. It is also capable of operating other computers. The operation of a computer is divided into four basic functions:
stores and processes,
During this learning period, the engine may ______,_______, or have a loss of power. The average learning period lasts for ______ of driving.
surge, idle fast, 5 miles
The length of time the air pump is operating depends on the _________ of the engine. Once the catalyst is warmed up, the PCM signals the relay to shut down the ________. The PCM also ________ the air-injection bypass solenoid, which allows the air diverter valves to close.
temperature, air pump, de-energizes,
Mode 7 is the monitoring of _________ for continuously monitored systems. A two-trip DTC may be displayed here after the first failure as a _________, but the information may not be accurate until confirmed by another _______. If the vehicle shows a failure here after one trip, the technician should make sure that the vehicle is OK before returning it to the customer.
test results, pending code, failure
The PCM output that controls the throttle actuator control (TAC) commands the ___________ to sweep during engine cranking to check the _______ and _________.
throttle, TPSs, electric motor actuator.
When a fuel system problem causes the PCM to make large fuel trim corrections for an excessive __________, the fuel system monitor sets a _____ and illuminates the _____ if the fault occurs on two consecutive ________.
time period, DTC, MIL, drive cycles
The ROM also contains calibration tables regarding specific engine, ___________ , and differential specifications.
transaxle or transmission
Thousands of miniature ___________ are contained in the microprocessor. These transistors act as electronic _________ that are either on or off.
transistors and diodes, switches
To complete a drive cycle, all ______ must be completed. The ______ monitor must be completed after the other monitors in a drive cycle. A steady throttle opening between ______mph and _____ mph for 80 seconds is required to complete the catalyst efficiency monitor.
trip monitors, catalyst, 40, 60
The AIR system operation can be verified by turning the AIR system on to inject air ________ of the oxygen sensor while monitoring its signal. Current designs inject air into the _________ when the engine is in open loop. This extra air helps heat the ________ for proper operation. The pump runs for up to 2 minutes after a cold start.
upstream, exhaust manifold, converter
The heated oxygen sensor monitor checks the voltage signal frequency of the _______ HO2S. Excessive time between signal voltage frequencies indicates a ________.
upstream, faulty sensor.
When the AIR flow to the exhaust manifold is turned on, the sensor's _____ should decrease and the short-term FT should indicate a _______ condition. The secondary AIR system monitor illuminates the MIL and stores a DTC in the PCM's ________ if the AIR system fails the ________ on two consecutive trips.
voltage, leaner, memory, active test
The AIR system is monitored with passive and active tests. During the passive test, the _______ of the pre-catalyst HO2S is monitored from ________ to _________ operation. The ______ is normally on during this time.
voltage, start-up, closed-loop, AIR pump
The microprocessor can _________ information from a keep alive memory (KAM).
write and read
