Ignition Diagnostic Monitor (IDM)

The Ignition Diagnostic Monitor (IDM) is a tachometer signal received from the ignition coil through a 22K ohm resistor. It is not an input device. The 22K ohm resistor block is located between the E-core coil and the Electronic Control Assembly (ECA). This resistor reduces the level of the tachometer signal voltage the ECA is capable of using (approximately 6-12 volts).

The ECA receives this tachometer signal and compares it to the Profile Ignition Pickup (PIP) signal. If for some reason the tachometer signal is interrupted, a continuous (memory) code will be registered in the memory of the ECA. This code indicates that sometime during recent operation the ECA received a PIP signal input without receiving a corresponding tachometer signal input.