No Crank Reference Signal at PCM

Name of Code:
No Crank Reference Signal at PCM

When Monitored:
With the ignition in either the start or run position and battery voltage between 4-15 volts.

Set Condition:
No crankshaft position sensor signal is detected when engine vacuum is present or cam signals are present.

Theory of Operation:
The crankshaft position sensor is a hall effect type sensor used to detect the crankshaft's speed and position. The PCM supplies 8 volts and a sensor ground to the CKP sensor. The crankshaft position sensor signal circuit has a 5-volt pull-up from the PCM. The sensor signal is created by the slots cut in the flywheel passing under the sensor. When a slot is under the sensor, the signal is high (5v). When the metal between the slots is under the sensor, the signal is low (0.3v).

Possible Causes:
- Open or shorted 8-volt supply circuit
- Open sensor ground
- Open or shorted signal circuit
- Excessive clearance between the sensor and flywheel
- Damaged flywheel
- Failed sensor
- Failed PCM