ICM And CKP/CMP Sensor Circuit Wiring Diagram (2003-2005 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: 2003, 2005, 2005.

Ignition Control Module (ICM)

The ignition control module (ICM) is the component that ties the entire ignition system together. It powers the crankshaft position sensor, monitors the signals it produces, determines which ignition coil should fire, and sends crankshaft position and engine speed information to the PCM.

The PCM then uses that information, along with inputs from other engine sensors, to control spark timing and fuel injection. If the ICM loses the crankshaft position sensor signals, it can't trigger the ignition coils, which usually results in a cranks-but-doesn't-start condition.

The crankshaft position sensor is actually two Hall-effect sensors housed in a single assembly. As the crankshaft rotates, two interrupter rings mounted behind the crankshaft balancer create digital ON/OFF signals that the ignition control module uses to track crankshaft position and engine speed.

We've got to have both of these signals for the ignition system to work correctly. If one of them disappears because of a sensor, wiring, or ignition control module problem, the ignition coils won't fire when they should.

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 provides the PCM with a synchronization signal that identifies when cylinder #1 is on its power stroke. The PCM uses this information to control sequential fuel injection.

One thing to keep in mind is that a bad CMP signal usually won't keep the engine from running. The PCM can switch to a backup operating strategy, although it'll usually set a diagnostic trouble code.

A very common mechanical failure on these engines is the magnet (that's attached to the camshaft sprocket) falls off from its plastic carrier (it become brittle and breaks with age). When the magnet falls off, the CMP sensor has nothing to detect, making it look like the sensor has failed when the real problem is the missing magnet.

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.