How Trouble Codes Are Set

SETTING CODES

The PCM has been programmed to verify that circuit parameters remain within the acceptable range established for each monitored circuit.

If a circuit parameter is detected outside of limits and ALL other Arming Conditions are met, a corresponding DIAGNOSTIC TROUBLE CODE (DTC) will be stored in PCM memory.

A DTC for will not be set unless ALL of the arming criteria needed to set the code have been met.

Example;

Assume the arming criteria for a sensor circuit DTC include requiring the engine to operate between 750 and 2000 RPM.

- If the sensor output circuit shorts to ground when engine RPM is ABOVE 2400 RPM,

- Then a diagnostic trouble code will not be entered into memory, (because the condition does not occur within the specified RPM range).

Arming Criteria

- Engine RPM

- Engine Temperature

- Input Voltage To The PCM

DISPLAYING CODES

Trouble codes stored in PCM memory can be displayed in two ways;

1. Cycling the ignition key On - Off - On - Off - On, and observing the Check Engine light.

2. Through a scan tool connected to the vehicle data link connector.

Note: SEE EXTRACTING TROUBLE CODES, for more information.

CLEARING CODES

The PCM will cancel DTC's after 51 vehicle key ON/OFF cycles, if the problem is repaired or ceases to exist.

SEE CLEARING TROUBLE CODES, for more information.