Diagnostic System: Notes
WARNING: This page is about a different car, the 1998 Pontiac Grand Prix, 1998 Chevrolet Monte Carlo, 1998 Chevrolet Lumina, and 1998 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
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/VCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM/VCM 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 as intermittent failures.
There are 4 types of DTC category:
- Type "A" Emissions related, turns on MIL the first time DTC sets.
- Type "B" Emissions related, turns on MIL if fault is active for 2 consecutive driving cycles.
- Type "C" Non-emissions related, does not turn on MIL, but will turn on SERVICE light.
- Type "D" Non-emissions related, does not turn on MIL or SERVICE light.