Vehicle: 1997-2002 Ford F-150 4.2L, 4.6L and 5.4L; and 1996 Ford F-150 5.0L

Symptom: After replacing the Crankshaft Position Sensor (CKP) and/or connector to correct another problem, the engine turns over, but does not start.

The fuel injectors pulse a couple of times when the engine starts cranking, then they stop pulsing. There is an rpm reading on the scan data for a split second, then it goes to zero. There is no spark.  

Problem: Reversed Crankshaft Position Sensor (CKP) wiring

Test & Fix: This is the exact symptom of reversed polarity on the CKP sensor wires. It may be due to the wires being installed in the connector incorrectly during a terminal replacement, or a sensor that was installed has reversed polarity.

To Repair: At the CKP connector, remove the grey and blue wires from their respective terminals and reverse them in the connector and recheck for proper operation.

Courtesy of Identifix.

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