C2.4 Tier 4 Final Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the primary engine speed/timing sensor. Also use this procedure if a problem is suspected with the secondary engine speed/timing sensor. Use this procedure to troubleshoot the electrical system if a diagnostic code in the table is active or easily repeated.

Table 1

Diagnostic Trouble Codes
Code	Description	Conditions Present	Response
636-2	Crankshaft position sensor pulse number error	Open circuit or short circuit of sensor / harness. Battery voltage is normal Sensor supply voltage VCC# is normal Engine is not stalled Pulse count per rotation is not 58 teeth for 10 times or more. Faulty starting. Engine vibration increases slightly.	Engine derates 25% Warning Level 2
636-8	No crankshaft position sensor signal	Open circuit or short circuit of sensor / harness. Failure of sensor. Battery voltage is normal Sensor supply voltage is normal Engine is not stalled. No recognition of crankshaft sensor pulse for 10 times or more. Faulty starting. Engine vibration increases slightly.
636-7	Engine Position Sensor – Large phase shift between Camshaft and Crankshaft position sensors	Large phase shift between NE pulse and G pulse Battery voltage is normal Sensor supply voltage VCC# is normal Crankshaft and crankshaft signals are normal Phase difference between NE pulse and G pulse is within +30 and - 20 degree for 2 times or more.
723-2	Camshaft sensor Pulse Number Error	Open circuit or short circuit of sensor / harness. Failure of sensor. Battery voltage is normal Sensor supply voltage VCC# is normal Engine is not stalled Pulse count per rotation is not 3 teeth for 4.4 rotations of crankshaft sensor pulse. Engine hesitates at start-up.	None
723-8	No Input of Camshaft Position Pulse	Open circuit or short circuit of sensor / harness. Failure of sensor. Battery voltage is normal Sensor supply voltage VCC# is normal Engine is not stalled No recognition of Camshaft sensor pulse for 4.4 rotations of crankshaft sensor pulse. Engine hesitates at start-up.	None

The crankshaft position sensor is the primary speed/timing sensor. The camshaft position sensor is the secondary speed/timing sensor. The position sensorare used to determine the piston height and engine speed.

If the engine is running and the signal from the primary engine speed/timing sensor is lost, the engine will derate. Loss of the signal from the secondary engine speed/timing sensor during engine operation will not result in any noticeable change in engine performance.

During startup the loss of either the crankshaft or camshaft speed/timing sensor will result in hard starting.

The loss of both the crankshaft and camshaft speed/timing sensors will result in no start or the engine will stop.

Illustration 1	g06111910

Note: 2 and 8 codes are detecting an open circuit or short circuit of the sensor or the harness. These are almost always harness-related.

Note: 7 codes measure a large phase shift between the crankshaft position sensor and the camshaft position sensor.

Table 2

Troubleshooting Test Step	Value	Expected Results
1. Check Supply Voltage at the Sensor Connector A. Turn the keyswitch to the OFF position. B. Disconnect the crankshaft position sensor. C. Turn the keyswitch to the ON position. D. Measure the voltage between terminals 1 and 3 on the harness side. The voltage should be 5V.	5 VDC	Result: The voltage was OK. Proceed to Test Step 2. Result: The voltage was NOT OK. There is a problem in the wiring harness. Replace the engine harness.
2. Remove the Sensor A. Check for signs of contact with the sensor or magnetic material.	Sensor	Result: There is no magnetic material. Replace the sensor. Result: There is magnetic material. Clean off sensor and reinstall. Confirm that the issue is resolved. Determine the source of the magnetic material if needed.

If this procedure did not correct the issue, contact your Technical Communicator (TC).