Diagnostic System

The ECM of the C-4 system is equipped with a self-diagnostic system which detects system failures or abnormalities. These failures will illuminate a test bulb (connected to ECM terminal "R"). Malfunctions are recorded as "hard failures" or "intermittent failures".

"Hard failures" cause test bulb to glow and remain on until malfunction is repaired. If test lamp remains on during vehicle operation, cause of malfunction MUST be determined.
"Intermittent failures" cause test bulb to flicker or go off when fault no longer exists, but a corresponding trouble code will be retained in ECM memory until battery voltage is removed.

As a routine system check, the test bulb will be illuminated when ignition switch is turned on without engine being cranked. When engine is started, the bulb will go out after a few seconds if no "hard failure" is detected.

NOTE: Trouble codes will be recorded at various operating times. Some codes require operation of engine at partial throttle for 5-18 minutes, before being diagnosed and recorded in memory.