P1391 Fault Code on 2000 Jeep Cherokee: Common Causes and Solutions
I'm experiencing a P139-1 diagnostic code on my 2000 Jeep Cherokee. I've reset the Check Engine light using an OBD II scanner, but the warning returns shortly after. What are the most frequent causes of this fault code? A local auto parts store provided a long list of potential issues, which makes it hard to pinpoint the root cause. My vehicle has 198,000 miles on the odometer—could this indicate an engine-related problem or is it more likely a sensor or wiring issue?
SYMPTOM: P1391 - INTERMITTENT LOSS OF CRANKSHAFT POSITION (CKP) OR CAMSHAFT POSITION (CMP) SENSOR SIGNAL WHEN MONITORED CONDITION: Triggered when the failure counter reaches 20 over two consecutive driving trips. POSSIBLE CAUSES: - CMP sensor out of phase or misaligned - Damaged tone wheel or flex plate (crankshaft) - Damaged tone wheel or pulse ring (camshaft) - Irregular lab scope pattern in CMP signal - Intermittent CKP signal loss when wiring is manually wiggled - Irregular lab scope pattern in CKP signal - Intermittent wiring harness fault - Intermittent CMP signal loss when wiring is wiggled - Faulty sensor connectors or wiring - Camshaft position sensor failure - Crankshaft position sensor connector or wiring issues Note: Intermittent problems are common—first check all connectors and wiring. Without a proper scan tool and lab scope or voltmeter, diagnosis remains speculative. Most cases involve connector or wiring faults, followed by crankshaft or camshaft sensors. What driveability symptoms do you notice? How frequently does the code appear?