P1391: How to Diagnose & Fix — Loss of Cam/Crank Position Sensor Signal — Intermittent Condition
2 vehicles · 2 makes · $100-$600 repair
How to diagnose and fix P1391: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Dodge Intrepid · 1993–2004
The Hall-effect camshaft and crankshaft position sensors (and their connectors) on Intrepid engines degrade with heat and fail intermittently, cutting spark and fuel without warning. Owners report sudden stalling while driving, engines that die after warming up and restart once cooled, and intermittent crank-but-no-start conditions. Chrysler addressed start/stall and no-start conditions in service bulletin coverage (SB 195966, May 1999), and the same defect is documented across the LH platform including the Chrysler Concorde.
Common Symptoms
- Engine stalls suddenly while driving, then restarts after cooling down
- Intermittent crank-but-no-start, especially when hot
- Stumbling, jerking, or engine misses under load
- Check engine light with cam/crank sensor codes
- Tachometer drops to zero just before the stall
How to Fix
Replace the failed camshaft and/or crankshaft position sensor and inspect the connector and wiring for heat damage; many shops replace both sensors together since they fail similarly. It is an inexpensive bolt-in repair once correctly diagnosed.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Mopar 4609086AF camshaft-position sensor
Replace only when scope/scan testing confirms cam-sensor or circuit failure Fitment: Confirm exact year/engine; the 1993-2004 issue span does not use one cam sensor Live OEM direct product page when checked
- Mopar 4609009 crankshaft-position sensor
Replace a failed crank sensor after heat-related signal loss is reproduced Fitment: Use only for catalog-confirmed engine/year applications Live OEM direct product page when checked
- Mopar 4727451AA crankshaft-position sensor
Alternate engine/year sensor branch Fitment: Confirm installed engine and connector before purchase Live OEM direct product page when checked
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Sources for this issue (1)
Jeep Liberty · 2002–2012
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)
Find P1391 by make
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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?
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.
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?
Repair costs for P1391 range from $100 to $600, depending on the vehicle and root cause.
Which vehicles are affected by P1391?
Au7o has documented P1391 across 2 vehicle models from 2 manufacturers: Dodge, Jeep.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.