ICM And CKP/CMP Sensor Circuit Wiring Diagram (1994-1995 3.8L V6 Buick LeSabre)

APPLIES TO: This ignition control module (ICM), CKP and CMP sensor circuit wiring diagram applies to the following vehicles:

• 3.8L V6 Buick LeSabre: 1994, 1995.

Ignition Control Module (ICM)

The ignition control module (ICM) is the "middleman" between the crankshaft position sensor, camshaft position sensor, ignition coils, and the PCM.

Its first job is to power the crankshaft position sensor and interpret the signals it produces. Using those signals, the ICM figures out which ignition coil needs to fire and when. Once the engine starts, it continues sending crankshaft position and engine speed information to the PCM so the PCM can control ignition timing and fuel injection.

The thing to keep in mind is that if the ICM doesn't receive the proper crankshaft position sensor signals, it won't trigger the ignition coils. The end result is no spark and a cranks-but-doesn't-start condition.

Crankshaft Position (CKP) Sensor

The crankshaft position sensor is actually two Hall-effect sensors built into one housing. It works together with two interrupter rings mounted behind the crankshaft balancer.

As the crankshaft turns, the interrupter rings repeatedly block and unblock the magnetic field inside the sensor. This creates two digital ON/OFF signals that the ignition control module uses to determine crankshaft position and engine speed.

We've got to have both of these signals for the ignition control module to correctly fire the ignition coils. If either signal is missing, the engine usually won't start.

CKP SENSOR TESTS: How To Test The CKP Sensor With A Multimeter (1994-2005 3.8L V6 Buick LeSabre).

Camshaft Position (CMP) Sensor

The camshaft position sensor lets the PCM know when cylinder #1 is on its power stroke. The PCM uses this information to synchronize sequential fuel injection.

The good news is that the engine will usually continue to run even if the CMP sensor signal is lost. The PCM switches to a backup strategy for injector timing, although it may set diagnostic trouble code.

One very common problem on these engines isn't the sensor itself. It's the small magnet mounted to the camshaft sprocket. The plastic holder that secures the magnet is known to break with age, allowing the magnet to fall off. When that happens, the CMP sensor can no longer generate its signal even though the sensor itself is perfectly good.

You can find a complete list of 3.8L V6 Buick LeSabre tutorials and wiring diagrams in this index:

• 3.8L V6 Buick LeSabre Index of Articles.