2004 Jeep Grand Cherokee 4.7L Engine P1391 Fault: Loss of Camshaft/Crankshaft Sensor Despite Replaced Sensors
I own a 2004 Jeep Grand Cherokee Overland with the 4.7L HO engine. After installing a completely rebuilt engine, I'm now encountering a persistent Diagnostic Trouble Code (DTC) P1391 — indicating an intermittent loss of camshaft or crankshaft position sensor signal. I have already replaced both the camshaft and crankshaft position sensors twice, but the issue persists. The engine runs smoothly under light loads and at speeds below 2500 RPM. However, when accelerating quickly, it boggs down as if experiencing excessive fuel delivery. I've also replaced the throttle position sensor with no improvement. Despite these efforts, the P1391 code remains active. Any additional troubleshooting steps or recommendations for diagnosing this issue would be greatly appreciated.
P1391 - INTERMITTENT LOSS OF CAMSHAFT OR CRANKSHAFT POSITION SENSOR First, use an OBD2 scanner to confirm the code and check for any related codes. The primary suspect is often a SYNC issue between sensors. Recommended diagnostic steps: - Verify that the camshaft and crankshaft position sensors are out of sync using a lab scope or signal graphing tool. - Perform a thorough harness inspection for loose connections, corrosion, or damage. - Inspect the tone wheel (camshaft) and pulse ring (crankshaft) for wear or physical damage. - Check all wiring harnesses for fraying or intermittent contact points. - Test both camshaft and crankshaft position sensor signals with a lab scope to identify intermittent faults. Note: Even if sensors are replaced, the root cause may lie in mechanical alignment, signal interference, or sensor mounting issues. A proper signal graph is essential to confirm the source of the P13或 code.