P1391 on Jeep: How to Diagnose & Fix
Loss of Cam/Crank Position Sensor Signal — Intermittent Condition
1 Jeep model · 1 documented issue · 1 critical · $120-$600 repair
P1391 on Jeep by model: symptoms, diagnosis and fix
Libertys of both generations lose the crank reference signal to the PCM, setting P0320 and shutting the engine off without warning - owners describe the vehicle simply dying at speed, sometimes restarting immediately and sometimes not for hours, and often producing a limp-mode condition. The fault is heat-sensitive, so it typically appears after the engine is warmed and is hard to reproduce cold at a shop. The forum record contains a real diagnostic warning: on Chrysler powertrains, crank and cam sensor codes are misleading, and the failure is frequently in the connector or the harness (oil-contaminated pins, chafed wiring) or in the PCM rather than in the sensor itself - multiple owners report P0320 returning immediately after a new sensor. Stalling in traffic makes this a safety issue, not just a driveability complaint.
Common Symptoms
- Engine stalls without warning while driving
- Intermittent crank but no start, often when hot
- Rough idle and hesitation
- Check engine light for no crank reference signal
- Vehicle enters limp mode
- Restarts normally after cooling down
How to Fix
Scan and record all codes - P0320 arriving with P1391 or P0340 changes the diagnosis. Before replacing the sensor, inspect the crank sensor connector and pigtail for oil intrusion, spread or corroded terminals, and chafe where the harness passes near the bellhousing; clean and repair as needed. Then replace the crankshaft position sensor with a Mopar or equivalent-quality unit - cheap aftermarket crank sensors are a documented repeat-failure source on these vehicles. If the code returns with a known-good sensor and a sound harness, the PCM is the remaining suspect. No recall covers this.
Sources for this issue (3)
P1391 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1391 mean on a Jeep?
P1391 stands for "Loss of Cam/Crank Position Sensor Signal — Intermittent Condition." P1391 is a manufacturer-specific code used primarily by Chrysler, Dodge, and Jeep indicating an intermittent loss of signal from the camshaft position (CMP) sensor or crankshaft position (CKP) sensor. The PCM uses these signals to determine engine timing for ignition and fuel injection, so a dropout can cause hesitation, stalling, or a no-start condition. Note that on a few other makes (e.g., some Chevrolet/GM applications) P1391 can instead refer to a wheel-speed/G-sensor circuit fault. On Jeep it is documented across 1 model: Liberty.
What are the most common causes of P1391?
The most common causes of P1391 are: Failing crankshaft position (CKP) sensor — often drops out when hot, then recovers when cool, Failing or intermittent camshaft position (CMP) sensor, Damaged, corroded, or loose sensor wiring/connectors or a poor ground, Low-quality aftermarket (non-OEM) cam/crank sensor causing the code to return after repair, Damaged tone/reluctor wheel teeth on the crankshaft, camshaft, or flexplate, Intermittent open or short in the sensor signal circuit to the PCM. The specific cause varies by vehicle.
How much does it cost to fix P1391 on a Jeep?
Published repair estimates on Jeep range from $120 to $600 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P1391 on a different make?
View P1391 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.