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.
