Monitored Circuits

The PCM is able to monitor and identify most driveability related trouble conditions. Some circuits are directly monitored through PCM feedback circuitry. In addition, the PCM monitors the voltage state of some circuits and compares those states with expected values. Other systems are monitored indirectly when the PCM conducts some type of a rationality test to identify problems.

Although most subsystems of the powertrain control module are either directly or indirectly monitored, there may be occasions when diagnostic trouble codes are not immediately identified.

For a trouble code to set, specific conditions must be met and unless these conditions are encountered, a code will not set. For example, the Speed Control Solenoid Circuits trouble code will not set unless the system is active (speed control is turned on, the brake is off and the vehicle is travelling at more than 35 mph).

When a trouble code identifying a problem in an emission related system is set, the Check Engine/Malfunction Indicator lamp in the dash will turn on. Conversely, any other trouble code will set without illuminating the Check Engine/Malfunction Indicator lamp.