ICM And 3X CKP Sensor Circuit Wiring Diagram (1994-1995 3.1L V6 Buick Century)

APPLIES TO: This ignition control module (ICM) and 3X CKP sensor circuit wiring diagram applies to the following vehicles:

• 3.1L V6 Buick Century: 1994, 1995.

The 3X (7X) Crankshaft Position Sensor

On 1994-1995 models, GM refers to this sensor as the 3X crankshaft position (CKP) sensor. In later model years, it's called the 7X CKP sensor. Regardless of its name, it's the same 2-wire magnetic pickup sensor.

The sensor is mounted low on the rear of the engine block, below the rear exhaust manifold (the side of the engine facing the firewall). It reads the crankshaft reluctor ring and sends its AC voltage signal directly to the ignition control module (ICM). It does not connect directly to the PCM.

Without this signal, the ignition control module cannot begin firing the ignition coils, which means the engine will crank but won't start.

3X CKP SENSOR TESTS: How To Test The 7X Crankshaft Position Sensor (1994-2005 3.1L V6 Buick Century).

The Ignition Control Module (ICM)

The ignition control module is mounted on top of the rear valve cover underneath the three ignition coils.

During cranking, the ICM uses the CKP sensor's signal to determine which ignition coil to fire. Once the engine is running, the ICM also generates the 3X crankshaft reference signal that it sends to the PCM.

The PCM uses this 3X reference signal to calculate engine RPM, control fuel injector operation, and help determine ignition timing. This is a digital ON/OFF signal that occurs three times for every crankshaft revolution.

ICM DIAGNOSTIC TESTS: Testing The Ignition Module And Crank Sensor (GM 3.1L, 3.4L) (at: easyautodiagnostics.com).

Ignition Coils

This ignition system uses three individual twin-tower ignition coils mounted directly on top of the ignition control module (ICM). Each coil fires two spark plugs at the same time using a waste-spark ignition system.

Each ignition coil receives battery power on one terminal whenever the ignition switch is in the ON position. The ignition control module completes and interrupts the Ground path on the other terminal to fire the coil at precisely the right moment.

The most common ignition coil failures are:

• One tower produces spark while the other tower does not.
• Neither tower produces spark because the entire ignition coil has failed.

Since each coil is serviced separately, you only need to replace the failed coil instead of the entire coil assembly.

IGNITION COIL TESTS: How To Test The Ignition Coil Packs (GM 3.1L, 3.4L) (at: easyautodiagnostics.com).

Other 7X CKP Sensor Wiring Diagrams

• ICM And 7X CKP Sensor Circuit Wiring Diagram (1996 3.1L V6 Buick Century).
• ICM And 7X CKP Sensor Circuit Wiring Diagram (1997 3.1L V6 Buick Century).
• ICM And 7X CKP Sensor Circuit Wiring Diagram (1998-2005 3.1L V6 Buick Century).

More 3.1L V6 Buick Century Tutorials

You can find a complete list of 3.1L V6 Buick Century tutorials and wiring diagrams in this index:

• 3.1L V6 Buick Century Index of Articles.

Here's a sample of the tutorials you'll find in the index:

• How To Test The TPS With A Multimeter (1997-2005 3.1L V6 Buick Century).
• Common Causes Of Spark Plug Failure (1994-2005 3.1L V6 Buick Century).
• How To Test For A Blown Head Gasket (1994-2005 3.1L V6 Buick Century).
• How To Test Engine Compression (1994-2005 3.1L V6 Buick Century).