Chapter 72: Engine Management and On-Board Diagnostic Systems
What is the typical voltage for a stoichiometric ratio as indicated by an oxygen sensor?
0.45 volts
When the oxygen sensor reaches it's operating temperature, around ___, it sends an output voltage to the control unit to signal whether the mixture is richer or leaner than a lambda value of 1.
600
The PCM of an engine is comprised of all of the following parts EXCEPT:
A Feedback Control Section
A DTC indicates that a vehicle has experienced all of these EXCEPT:
A broken "hard part"
What does it mean if the malfunction indicator lamp (MIL) is flashing?
A catalyst damaging event is occurring.
If an emissions-related sensor or component is monitored by the OBD-II system and indicates emissions would exceed 1.5 times the standard limit, what happens?
A diagnostic trouble code (DTC) is set, the information is stored, and the malfunction indicator lamp (MIL) is illuminated.
Which of the following is most likely to cause an excessively negative long-term fuel trim condition?
A leaking fuel injector
When diagnosing with a scan tool, which of the following is the best time to clear the diagnostic trouble codes (DTCs)?
After the diagnosis is complete or freeze frame data is saved
What is false air?
Air that has not been measured by the mass airflow (MAF) sensor
Any of these may be required to diagnose a vehicle when diagnostic trouble codes (DTC's) have NOT been set EXCEPT:
An analog ohmmeter
High priority faults that require continuous monitoring include all of the following EXCEPT:
An oxygen sensor monitor
The ___ specifically measures the pressure on the air around us.
BARO
Airflow measurement is being discussed. Technician A states that the speed density method relies on several engine sensors and is then calculated based on a preprogrammed data map. Technician B states that in types with a mass airflow (MAF), there can be no leaks in the intake tube or manifold after the sensor for the reading to be accurate. Who is correct?
Both
Diagnostic trouble codes (DTCs) are being discussed. Technician A states that a pending DTC is set when the failure is damaging the catalytic converter. Technician B states that DTCs can be cleared by the technician, or they can be cleared automatically by passing the test that set the DTC a specific number of times consecutively. Who is correct?
Both
Powertrain control modules (PCMs) are being discussed. Technician A states that the PCM acts as the brain of the engine management system by monitoring inputs and commanding outputs. Technician B states that the PCM refers to a data map to make decisions. Who is correct?
Both
Tech A says crankshaft position sensors can be a magnetic pickup-style sensor. Tech B says crankshaft position sensors can be a Hall-effect sensor. Who is correct?
Both
Tech A says sometimes MAF sensors can be cleaned when they have a buildup of dirt and contamination. Tech B says that some manufacturers specifically say not to clean their MAF sensors. Who is correct?
Both
Tech A says that OBD-I systems were typically limited to well under 100 possible faults. Tech B says that OBD-II standardized items such as location and pin assignments for the diagnostic connector. Who is correct?
Both
Tech A says that a drive-by-wire refers to an engine that utilizes an electronically controlled throttle. Tech B says that an electronically controlled throttle uses a position sensor on the accelerator pedal to calculate the drivers desired throttle position. Who is correct?
Both
Tech A says that a relay is a controlled device that receives signals from the PCM. Tech B says that a solenoid is a controlled device that receives signals from the PCM. Who is correct?
Both
Tech A says that output drivers in the PCM typically send either simple on/off signals or pulse-width-modulated signals to the actuators, depending on the actuator being controlled. Tech B says that in many cases, the software in the PCM's memory can be updated by uploading software updates, called a reflash process. Who is correct?
Both
Tech A states that simple scan tools from the 1980's could read and erase fault codes. Tech B states that modern scan tools can display sensor data in a graphical format. Who is correct?
Both
Which of the following sensors is used to report the number one piston on the compression stroke?
Camshaft Position Sensor
In an engine management system, work is done by the actuators, which consist of all of the following EXCEPT:
Capacitors
Which of the following modes is used by technicians during a cranking sound diagnosis test to fool the engine into cranking without starting?
Clear Flood Mode
Continuous monitors are run for systems that could:
Contribute to major emissions failures.
Which of the following sensors are most involved in the control of ignition timing and injection sequencing?
Crankshaft Position Sensor
Which of the following sensors can the Powertrain Control Module (PCM) use to determine engine speed?
Crankshaft Position Sensor
On-board diagnostic (OBD) systems help the service tech do all of the following EXCEPT:
Determine exactly where faults exist.
Which of these is the best place to start gathering information and planning a diagnostic pathway based on suspected systems and components?
Diagnostic Trouble Codes (DTCs) and customer information
If the MIL flashes, it indicates that the:
Driver should stop the vehicle as soon as safely possible
___ monitors the system for leaks as well as the ability to purge the canister of vapors.
Evaporative System Monitor
A fault code that begins with the letter "P" would most likely address a fault in the:
Exhaust System
Cost and complexity increase with the level of ___ desired in a scan tool.
Features
All of the following statements with respect to freeze-frame data are true EXCEPT:
Freeze-frame data are saved for all DTC's stored in memory
Which of the following is NOT an example of an electric motor actuator?
Fuel Injector
Which of the following is a continuous monitor?
Fuel System Monitor
Which node of the PCM translates information from or to the other networks so that it can be shared between networks?
Gateway Mode
A vehicle previously set a diagnostic trouble code (DTC) and the malfunction indicator lamp(MIL) was illuminated. The vehicle was repaired and driven for a couple of weeks, but the codes had not been cleared. What type of DTC is stored in the powertrain control module (PCM)?
History Code
All of the following statements regarding DLC are true EXCEPT:
It's location is also now fairly standardized as being within 2' of the engine.
A(n) ___ sensor directly measures the mass of filtered air entering the engine.
MAF
Which sensor is responsible for measuring the amount of air entering an engine?
MAF Sensor
The ___ measures changes in engine speed and engine load in the intake manifold.
MAP
The barometric pressure (BARO) sensor works in conjunction with the ___.
MAP Sensor
Which of the following sensors provides information that is the most critical for proper air-fuel mixture, as well as ignition timing?
MAP Sensor
Which part of a powertrain control module retains diagnostic trouble codes (DTC's), freeze-frame data, and learned data?
Memory and storage section
The ___ continuously monitors either crankshaft speed or possible combustion chamber feedback that indicates misfiring cylinders.
Misfire Monitor
Which of the following is an example of a continuous monitor?
Misfire Monitor
Oxygen sensors are being discussed. Technician A states that early oxygen sensors could measure precisely how rich or how lean an engine was running. Technician B states that wide-band oxygen sensors can tell that the engine is rich or lean, but not how much. Who is correct?
Neither
Tech A says that any vehicle made after 1976 will use two oxygen sensors. Tech b says that oxygen sensors are located in the intake manifold. Who is correct?
Neither
Tech A says that in modern vehicles, an oxygen sensor is only positioned in the exhaust pipe after the catalytic converter. Tech B says that the oxygen sensor provides the electronic body control module with an electrical signal that relates to the amount of oxygen in the exhaust gas. Who is correct?
Neither
A bidirectional scanner can do which of the following?
Operate various components and systems for test purposes.
In many cases, the software in the PCM's memory can be updated by uploading software updates, called a ___ process.
Reflash
Which of the following is often used as an actuator to control other actuators when the computer needs to control a high-current load?
Relays
A(n) ___ is a device able to electronically communicate with and extract data from the vehicle's one or more onboard computers.
Scan Tool
In the engine management system, which of the following create input signals to the PCM?
Sensors
When DTC's are ___, the MIL will illuminate on the dash, indicating a fault.
Set
The speed-density method of determining the amount of air entering the engine takes into account all of the following EXCEP
Spark Knock
The purpose of the vehicle speed sensor is to measure the:
Speed of the vehicle
Which of these pollutants has not decreased at least 30% since 1970 due to the regulation and effectiveness of the OBD system?
Sulfur Dioxide
A fault code that begins with the letter "B" would MOST likely address a fault in the:
Taillight Circuit
A vehicle with a current P0128 diagnostic trouble code (DTC) is being discussed. Technician A states that the P means it is related to the powertrain system. Technician B states that the 0 means it is manufacturer specific. Who is correct?
Tech A
Diagnostic trouble codes (DTCs) and the malfunction indicator lamp (MIL) are being discussed. Technician A states that when a one-trip DTC sets, the MIL is illuminated immediately. Technician B states that if a catalyst damaging fault occurs, it will turn the MIL red rather than yellow. Who is correct?
Tech A
Pressure sensors are being discussed. Technician A states that a pressure sensor is typically mounted into the fuel tank. Technician B states that barometric pressure (BARO) sensors measure the temperature of the exhaust. Who is correct?
Tech A
Tech A says that a closed loop system means the ECM is receiving feedback and adjusting the fuel injector on time as needed. Tech B says that lean means there is not enough air in the air fuel mixture. Who is correct?
Tech A
Tech A says that an open loop is when the PCM ignores the oxygen sensor signals. Tech B says that a closed loop is when the PCM shuts off the fuel injectors during a collision. Who is correct?
Tech A
Tech A says that potentiometer type sensors create a variable voltage signal that corresponds to a specific condition. Tech B says that oxygen sensors are the potentiometer type. Who is correct?
Tech A
Tech A says that some GDI engines may have two fuel pressure sensors. Tech B says that most fuel pressure sensors are mounted in the fuel tank. Who is correct?
Tech A
Tech A says that the oxygen sensor is part of the feedback system for the engine management system. Tech B says that positive long-term fuel trims mean that the PCM is leaning out of fuel mixture from the base pulse-width setting. Who is correct?
Tech A
Fuel trim is being discussed. Technician A states that negative fuel trim can be caused by a vacuum leak. Technician B states that positive fuel trim can be caused by a restricted fuel filter. Who is correct?
Tech B
History codes are being discussed. Technician A states that history codes are any codes that have ever happened on the vehicle. Technician B states that history codes are saved in the powertrain control module's (PCM's) memory for 40 warm-up cycles. Who is correct?
Tech B
PCM actuators are being discussed. Technician A states that the throttle position sensor is an example of an actuator. Technician B states that a fuel injector is an example of an actuator. Who is correct?
Tech B
Tech A says that mass airflow sensors determine mass airflow based on engine speed and manifold pressure. Tech B says that some airflow sensors use a hot wire to determine mass airflow. Who is correct?
Tech B
Tech A says that speed density systems use vehicle speed and fuel density to determine injector pulse width. Tech B says that mass airflow systems use a sensor to measure the mass of the air entering the engine. Who is correct?
Tech B
Tech A says that the oxygen sensor measures the amount of oxygen entering the intake manifold. Tech B says that many oxygen sensors have a built-in heater to warm them up more quickly. Who is correct?
Tech B
In a vehicle, thermistors are used in various sensors related to:
Temperature
The feedback looping system in a three-way catalytic converter serves to adjust:
The Air-fuel ratio
Which feature allows sensor data readings to be accessed with a scan tool?
The Datastream
Accessories not installed by the original equipment manufacturer (OEM) can be difficult to diagnose for all of the following EXCEPT:
The warranty may have expired.
A resistor that changes it's resistance with changes of temperature is called a:
Thermistor
The potentiometer can be linear or circular in construction and has ___ electrical connecting points.
Three
Why is it important to run the monitors after repair?
To ensure that the fault does not immediately reoccur.
A scan tool detects a communications fault in the controller area network bus (CANbus). Which of these diagnostic trouble codes (DTC's) would MOST likely be stored?
U0021
The speed density method calculates the volume of air entering the engine, based on all of the following inputs EXCEPT:
Vehicle Speed
