Self-Diagnostic System: Description: Notes

NOTE: Powertrain Control Module (PCM) may also be referred to as Vehicle Control Module (VCM) in some diagnostic text and illustrations. Terms may be used interchangeably.

PCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM will store a Diagnostic Trouble Code (DTC) and, in most cases, illuminate the Service Engine Soon (SES) lamp, also called the Malfunction Indicator Light (MIL) located on instrument cluster. Malfunctions are recorded as hard failures or intermittent failures.

There are 4 types of DTC categories:

Type "A"

Emissions related. Illuminates MIL the first time DTC sets.

Type "B"

Emissions related. Illuminates MIL if fault is active for 2 consecutive driving cycles.

Type "C"

Non-emissions related. Does not illuminate MIL, but will illuminate SERVICE light.

Type "D"

Non-emissions related. Does not illuminate MIL or SERVICE light.