Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The 4X camshaft position (CMP) sensor circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, low reference circuit, and an output signal circuit. The CMP sensor is an internally magnetic biased digital output integrated circuit sensing device. The sensor detects magnetic flux changes of the teeth and slots of a 4-tooth reluctor wheel attached to the camshaft. As each reluctor wheel tooth rotates past the CMP sensor, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF DC voltage pulse of varying frequency, with 4 varying width output pulses per camshaft revolution that represent an image of the camshaft reluctor wheel. The frequency of the CMP sensor output depends on the velocity of the camshaft. The ECM decodes the narrow and wide tooth pattern to identify camshaft position. This information is then used to determine the optimum ignition and injection points of the engine. The ECM also uses CMP sensor output information to determine the camshaft relative position to the crankshaft, to control camshaft phasing, and for limp-home operation.

Important: The ECM detects engine movement by sensing the airflow through the mass air flow (MAF) sensor is more than 3 g/s, or by sensing crankshaft position (CKP) sensor pulses.

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With a DTC set, the engine may crank for an extended period of time at start-up.

With a DTC set, the engine may crank for an extended period of time at start-up.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Description and Operation

Electronic Ignition (EI) System Description

1. With the ignition OFF, inspect the engine wiring harnesses carrying the CMP sensor circuits for the following conditions:

•	Close routing of secondary ignition wires

•	Close routing of aftermarket electrical equipment

•	Close to solenoids, motors, and relays

⇒	Correct any wire harness routing or component placement conditions, if it is determined to be a possible source of electrical interference.

2. With the engine running, observe the CMP Sensor parameter using the scan tool. Operate the engine from idle up to 3,000 RPM. The CMP Sensor speed should match the Engine Speed parameter within 100 RPM.

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1. Ignition OFF, disconnect the 16-way engine harness to fuel injector harness connector.
2. Test for less than 1.0 ohm of resistance between ECM side of the low reference circuit and ground.

⇒	If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 volts between the ECM side of the 5-volt reference circuit and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Ignition ON, test for 4.8-5.2 volts between the ECM side of the signal circuit and ground.

⇒	If less than the specified range, test the affected signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the affected signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

5. Ignition ON, using a jumper wire connected to ground, momentarily touch the CMP sensor signal circuit repeatedly. The CMP active counter parameter should increment.

⇒	If the CMP active counter does not increment, replace the ECM.

6. Ignition OFF, inspect the wiring harness, from the 16-way connector to the CMP sensor, for any damage, opens, or shorts.

⇒	If the circuits test normal replace the CMP sensor.

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1. Ignition OFF, inspect the CMP sensor for looseness and correct installation.

⇒	If the sensor is loose, inspect the sensor and the O-ring for damage, replace as necessary.

2. Inspect the engine for the following conditions:

•	Engine oil for debris

•	Camshaft reluctor wheel for damage

•	The timing chain, tensioner, and sprockets for wear or damage

⇒	If debris is found in the engine oil, inspect the internal engine components to determine the cause. Repair or replace any worn or damaged components. Refer to Camshaft Timing Chain and Sprocket Cleaning and Inspection , and Camshaft and Bearings Cleaning and Inspection .

Important: You must perform the Circuit/System Testing before proceeding with Component Testing.

1. Inspect the CMP sensor for looseness and correct installation. Remove the CMP sensor from the engine and inspect the sensor and the O-ring for damage.

⇒	If the sensor is loose, incorrectly installed, or damaged; repair or replace the CMP sensor.

2. Connect the CMP Sensor connector to the CMP Sensor; turn ON the ignition, with the engine OFF.
3. Ignition ON and engine OFF. Observe the CMP Active Counter parameter on the scan tool; pass a steel object by the tip of the sensor repeatedly. The CMP Active Counter parameter should increment.

⇒	If the parameter does not increment, replace the CMP sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.