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 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.