Idm ???
Cargo Master
Joined: Mar 2001
Posts: 2,759
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From: Elk River, MN
Idm ???
You owe me, I had to really dig for this one:
The Ignition Diagnostic Monitor (IDM) signal is an input into the PCM. This signal is the voltage from the primary side of the coil (commonly known as TACH). When the coil is turned off to fire the spark plugs, a large flyback voltage (up to 400 volts) is generated on the IDM circuit by the coil discharge. The PCM interprets this positive voltage transition to mean that the coil fired. The coil signal is processed directly by the PCM through an external 22 K ohm resistor on push start TFI ICMs. The coil signal is processed internally on computer controlled dwell TFI ICMs, then sent on to the PCM as a digital signal. The PCM expects to see an IDM pulse for every SPOUT. It uses this information to determine if the ignition coil and other ignition components are working properly.
The Ignition Diagnostic Monitor (IDM) signal is an input into the PCM. This signal is the voltage from the primary side of the coil (commonly known as TACH). When the coil is turned off to fire the spark plugs, a large flyback voltage (up to 400 volts) is generated on the IDM circuit by the coil discharge. The PCM interprets this positive voltage transition to mean that the coil fired. The coil signal is processed directly by the PCM through an external 22 K ohm resistor on push start TFI ICMs. The coil signal is processed internally on computer controlled dwell TFI ICMs, then sent on to the PCM as a digital signal. The PCM expects to see an IDM pulse for every SPOUT. It uses this information to determine if the ignition coil and other ignition components are working properly.
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