Possible Causes
NOTE: The listed causes may not be a complete list of all potential issues and there may be other causes.
- Faulty crankshaft position sensor
- Crankshaft position sensor (CKP) harness is open or shorted
- Poor electrical connection in crankshaft position sensor (CKP) circuit
Description
The crankshaft position sensor (CKP) sends pulses to the powertrain control module (PCM) when the teeth of the reluctor wheel rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the operation of the ignition and fuel injector, and to time the interval between each CKP pulse. The PCM determines when excessive crankshaft speed variation occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in crankshaft speed. Some acceleration/deceleration is expected between each firing event, but if the crankshaft speed changes more than expected, the PCM interprets this as a misfire. The interval between CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult: – Crankshaft – Reluctor wheel – CKP sensor The PCM learns the variations during the crankshaft position system variation learn procedure. The PCM compensates for these variations when performing misfire detection calculations. Only a scan tool can command the PCM to perform the crankshaft position system variation learn procedure again. Perform the learn procedure after the following actions: – PCM replacement – Any operation or repair involving the crankshaft, CKP sensor, or CKP sensor/reluctor wheel air gap relationship – Engine replacement – Ignition switch is in ON position until battery is discharged.
How to Repair
Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
- Engine light on (or service engine soon warning light)
- Lack/loss of power
- Engine stalling