GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1996 🢒 Aurora 🢒 Engine 🢒 Engine Electrical 🢒 Ignition Control Module Replacement

Ignition Control Module Replacement L36 and L67

Ignition Control Module

The ICM performs the following functions:

    • Powers the dual CKP sensor internal circuits
    • Supplies the voltage signals that each respective hall effect pulses to ground in order to generate the 18X and 3X CKP sensor pulses
    • Determines the correct ignition coil firing sequence based on how many 18X transitions occur during a 3X pulse. This coil sequencing occurs at startup. The ICM remembers the sequence and continues to trigger the coils, in both the module and IC modes.
    • Cuts off the fuel delivery and the spark in order to prevent backfiring if reverse rotation is detected in the crankshaft
    • Sends a crankshaft reference (fuel control) signal to the PCM (The PCM determines engine RPM from this signal.)

Ignition Coils

Three twin tower ignition coils are individually mounted on the ICM. The system uses a waste spark method of distribution, where each coil fires two spark plugs simultaneously. Each coil is serviced separately.

Two terminals connect each coil pack to the ICM. The 20A F/P-IGN relay center fuse provides a fused ignition feed to each coil. The other terminal at each coil is individually connected to the ICM. The ICM completes and interrupts the primary circuit ground path to each coil at the proper time, which energizes each coil one at a time.

Ignition Control Module Replacement L47

The ignition control module (ICM) is located on top of the rear camshaft cover. The ICM performs sever functions:

    • It monitors the ON-OFF pulses produced by the tow crankshaft and the camshaft position sensor.
    • It crates a 4X and 24X reference signal (4X ref. hi and 24X crank) sent to the PCM for ignition control.
    • It creates a camshaft reference signal (1/2X cam hi) sent to the PCM for fuel injection control.
    • It provides a ground reference (ref. lo/cam lo) to the PCM.
    • It provides a means for the PCM to control spark advance (bypass and ignition control), called ignition control mode.
    • It provides a limited means of controlling spark advance without PCM input, called module mode.

The ICM is not repairable. When a module is replaced, the remaining components must be transferred to the new module. Refer to Ignition Control Module Replacement (Assembly) .