OBD II test
Which of the following is not necessary for the misfire monitor to set a code?
Engine speed within 150 rpm of when the fault was detected
An OBD II warm-up cycle is defined by engine coolant temperature:
Increasing 40° to at least 160°
In an OBD II system mode 6 is:
The on-board test of non-continuous monitored systems
A flashing MIL indicates:
a misfire that may damage the catalytic converter
Technician A says a type A misfire will set a trouble code on the first failure. Technician B says a type B misfire will set a trouble code on the first failure. Who is correct?
a only
If the third digit of a DTC is the number 1, the system has detected a problem with the ____________________ system.
air/fuel control
A pending code is one that:
as had one failure but has not had a second consecutive failure
Technician A says an OBD II trip is the same as a drive cycle. Technician B says a trip is a period of operation that allows a monitor to complete. Who is correct?
b only
Technician A says long term fuel trim works to bring short term fuel trim close to zero percent correction. Technician B says if a lean condition exists because of a vacuum leak, the long term fuel trim will have a plus (+) number on the scan tool. Who is correct?
both a and b
Technician A says the basic advantage of the snapshot feature on a scan tool is the ability to look at the existing conditions when a code was set. Technician B says GM failure reports do the same thing as a snapshot but also include any fault stored in memory, not just those related to the emissions-related circuits. Who is correct?
both a and b
Technician A says the comprehensive component monitor is used to check devices that do not have their own monitor. Technician B says the comprehensive component monitor also checks the wiring for shorts and opens. Who is correct?
both a and b
The MIL light of an OBD-equipped vehicle is flashing. Technician A says a spark plug wire may be shorted to ground. Technician B says a cylinder may have low compression. Who is correct?
both a and b
Which of the following is not part of comprehensive component monitoring?
catalyst efficiency
all of the following are OBD II continuous monitors, except:
catalyst efficiency
What sensor is used for misfire detection?
crankshaft
The signal that alerts the misfire monitor that a misfire may be occurring is provided by the:
crankshaft position sensor
A type A DTC will set a pending code on the first failure and the MIL is illuminated on the second consecutive failure.
false
Catalytic converter efficiency is measured by monitoring the hydrocarbon storage capacity of the converter during closed loop operation.
false
In an OBD II vehicle the technician may be able to erase trouble codes without erasing freeze frame data.
false
The catalyst monitor must be completed before the other five monitors are completed in a trip
false
The catalyst monitor must be completed before the other five monitors are completed in a trip.
false
catalytic converter efficiency is measured by monitoring the hydrocarbon storage capacity of the converter during closed loop operation.
false
the third digit of a DTC indicates whether the code is an SAE or manufacturer-specific code.
false
If the second character of an OBD II code is a 1 the code is ____________________.
manufacturer specific
Which of the following OBD-II test modes allows scan tools to access freeze frame data?
mode 2
Technician A says Mode 5 contains the tests for non-continuously monitored systems. Technician B says Mode 6 contains the oxygen sensor monitoring tests. Who is correct?
neither a nor b
The output voltage of a downstream O2 sensor is fluctuating when the engine is at operating temperature. Technician A says the catalytic converter is working efficiently. Technician B says the O2 sensor may need to be replaced. Who is correct?
neither a nor b
The AIR pump is normally used:
on startup
What is the term used to define the operating conditions that must be present during a second trip to set a code?
similar conditions
While discussing the numbering of HO2S sensors, Technician A says they are identified by their position in relation to the number 1 cylinder and their location relative to the converters. Technician B says HO2S sensors on the same side of the vehicle as the number 1 cylinder have a 1 prefix, and sensors mounted downstream from the converter have a 1 suffix. Who is correct?
tech a only
Technician A says PCMs in an OBD II system may have replaceable PROMs. Technician B says a new PCM will need to be flashed before it can be used on a vehicle. Who is correct?
tech b
Technician A says the elimination of the replaceable PROM chip was part of the OBD II legislation to prevent the use of aftermarket high-performance PROMs. Technician B says that many updates for engine performance concerns can be performed during service by changing the PROM chip. Who is correct?
tech b
Technician A says enabling criteria defines the criteria that must be met before the vehicle will enter closed loop. Technician B says enabling criteria defines the criteria that must be met in order for a monitor test to be completed. Who is correct?
tech b only
While discussing HO2S connector repair, Technician A says that contact cleaner should be used on the HO2S connector whenever an HO2S code is present. Technician B says the seals on the connector should be intact to present corrosion. Who is correct?
tech b only
What will happen if the AIR system delivers air to the exhaust manifold during closed loop operation?
the system will run too rich
The PCM has the option of turning the MIL off when the diagnostic test which caused the MIL to light passes for:
three consecutive trips
A type A misfire will typically cause the MIL to flash.
true
Adaptive strategy allows the computer to adjust to minor defects in the inputs and outputs.
true
All OBD II equipped vehicles use a 16 pin data link connector, with nine terminals defined by SAE.
true
Data links may be referred to as bus wires.
true
Enable criteria must be met in order for the PCM to run a system monitor.
true
In an enhanced evaporative system monitor, a missing fuel tank cap will cause the MIL to turn on.
true
OBD II systems note the deterioration of certain components before they fail.
true
OBD II systems use a minimum of two O2 sensors as a catalyst efficiency monitor.
true
The comprehensive component monitor strategy determines potential electronic inputs that could affect emission levels.
true
The fuel system monitor checks short-term fuel trim (STFT) and long-term fuel trim (LTFT) while the PCM is operating in closed loop.
true
enable criteria must be met in order for the PCM to run a system monitor
true
