Ignition Diagnostic Monitor (IDM)

PURPOSE
The Ignition Diagnostic Monitor (IDM), an output from the Ignition Control Module (ICM), provides diagnostic information about the ignition system and drives the vehicle's tachometer.

OPERATION
The Powertrain Control Module (PCM) receives the IDM signal and compares it to the Profile Ignition Pickup (PIP) sensor signal.

If for some reason the IDM signal is interrupted, a continuous code is registered in the PCM memory. The stored code indicates, that during recent engine operation the PCM received a PIP signal without receiving corresponding IDM input. When SPOUT is high, IDM is low, and when SPOUT is low, IDM is high.