Town Car V8-281 4.6L SOHC (1991)
Engine Control Module: Description and Operation
Ignition Diagnostic Monitor (IDM) Operation
The Ignition Diagnostic Monitor (IDM), an output from the ignition module, provides diagnostic information about the ignition system and drives the
vehicles tachometer. The Electronic Control Assembly (ECA) 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 ECA memory. The stored code indicates, that during recent
engine operation the ECA received a PIP signal without receiving corresponding IDM input.
