Self-Diagnostic System: Notes

WARNING: This page is about a different car, the 1996 Cadillac Seville, 1996 Cadillac Eldorado, and 1996 Cadillac DeVille. 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 panel. 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.