Exam 9: Strategies of On-Board Diagnostic Continuous Monitors

When does the fuel system monitor run, and what is its role?

As a result of a misfire, unburned hydrocarbons (HC) are exhausted from the combustion chamber into the exhaust system, where they enter the catalytic converter.

What causes a misfire to occur?

What values are constantly adjusted by the PCM to correct for rich/lean running conditions?

Technician A says that the catalyst efficiency monitor evaluates the catalyst's ability to store oxygen. Technician B says the comprehensive component monitor looks for circuit shorts and opens. Who is correct?

Technician A says the comprehensive component monitor continues to run until all sensors have been tested once. Technician B says the rationality test checks to see if the input values from a sensor make sense, based on the current operating conditions at the time the test is performed. Who is correct?

List the three separate monitors that make up the continuous monitors?

The continuous monitors act as a safety gate against emission system failure that could result in increased pollutants being emitted.

Technician A says the learned LTFT corrections are used as a new base line for STFT. Technician B says the STFT values are constantly adjusted by the PCM to correct for rich/lean running conditions. Who is correct?

Explain what Type B and Type C misfires are and what the PCM does to react to these types of misfires.

How does the PCM use short-term fuel trim (STFT) information?

Explain what the comprehensive component monitor is.

Technician A says the functional test observes the reaction of an output device to a command from the PCM. Technician B says with a scan tool you can access the Readiness Status menu to determine which monitors have run. Who is correct?

What are the basic causes of a cylinder misfire, and what adverse effect do they have on tailpipe emissions?

Technician A says a random misfire or a multiple cylinder misfire will be recorded as a P0300 code. Technician B says that a MIL that is flashing is an indication of an intermittent emission system failure that is not currently occurring. Who is correct?

The comprehensive component monitor begins to run shortly after the vehicle is started.

What type of logic does the comprehensive component monitor use when determining whether or not to set a DTC and illuminate the MIL?

When may the fuel system monitor not be allowed to run?

Technician A says the fuel system monitor may not be allowed to run if a pending code is stored. Technician B says the comprehensive component monitor will use one-trip logic when determining when to set a DTC and illuminate the MIL. Who is correct?

Which of the OBD II monitors checks circuit integrity?