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Component Tests and General Diagnostics



CRANKSHAFT POSITION SENSOR SYSTEM DIAGNOSIS

DIAGNOSTIC INSTRUCTIONS
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.




DIAGNOSTIC FAULT INFORMATION




TYPICAL SCAN TOOL DATA

CIRCUIT/SYSTEM DESCRIPTION
The crankshaft position (CKP) sensor circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, low reference circuit and an output signal circuit. The CKP 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 58-tooth reluctor wheel on the crankshaft. Each tooth on the reluctor wheel is spaced at 60-tooth spacing, with 2 missing teeth for the reference gap. The CKP sensor produces an ON/OFF DC voltage of varying frequency, with 58 output pulses per crankshaft revolution. The frequency of the CKP sensor output depends on the velocity of the crankshaft. The CKP sensor sends a digital signal, which represents an image of the crankshaft reluctor wheel, to the ECM as each tooth on the wheel rotates past the CKP sensor. The ECM uses each CKP signal pulse to determine crankshaft speed and decodes the crankshaft reluctor wheel reference gap to identify crankshaft position. This information is then used to determine the optimum ignition and injection points of the engine. The ECM also uses CKP sensor output information to determine the camshaft relative position to the crankshaft, to control camshaft phasing, and to detect cylinder misfire.

DIAGNOSTIC AIDS
- Inspect the CKP sensor connector and the ECM connector for corrosion.
- With a DTC set, the engine may crank for an extended period of time at start-up.

CIRCUIT/SYSTEM VERIFICATION
If DTC P0641 or P0651 are set diagnose those DTCs first.
1. With the ignition OFF, inspect the engine wiring harnesses carrying the CKP 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. Start the engine. Using the Live Plot function on the scan tool, select the CMP parameter. Change the minimum spec to 400 RPM, and the maximum spec to 4,000 RPM. Select the CKP sensor parameter. Change the minimum spec to 600 RPM, and the maximum spec to 3,300 RPM.
3. Observe the scan tool.
4. Quickly accelerate and release the accelerator pedal several time. Do not exceed 3,200 RPM. The graphed lines on the Live Plot display should track together across the screen.
- If the vehicle passes the Circuit/System Verification test, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records data list.

CIRCUIT/SYSTEM TESTING

IMPORTANT: You must complete the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Disconnect the CKP sensor connector.
2. Test for less than 1 ohm of resistance between 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 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 signal circuit and ground.
- If less than the specified range, test 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 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 CKP sensor signal circuit repeatedly. The CKP Active Counter parameter should increment.
- If the CKP Active Counter parameter does not increment, replace the ECM.
6. Ignition OFF, inspect the CKP sensor for looseness and correct installation
7. Touch the jumper wire to the CKP sensor signal circuit repeatedly at the connector. The CKP Active Counter parameter should increment.
- If the sensor is loose, inspect the sensor and the O-ring for damage, replace as necessary.
8. Inspect the engine for the following conditions:
- Engine oil for debris
- Crankshaft 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.

COMPONENT TESTING

IMPORTANT: You must complete the Circuit/System Testing before proceeding with Component Testing.

1. Remove the CKP sensor from the engine and inspect the sensor and the O-ring for damage.
2. Connect the CKP Sensor connector to the CKP Sensor; turn ON the ignition, with the engine OFF.
3. Observe the CKP Active Counter parameter on the scan tool; pass a steel object by the tip of the sensor repeatedly. The CKP Active Counter parameter should increment.
- If the parameter does not increment, replace the CKP sensor.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Crankshaft Position Sensor Replacement for CKP sensor replacement
- Control Module References for ECM replacement, setup, and programming Verification Tests Programming and Relearning

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