P1391
CMP or CKP Signal Intermittent Condition
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The P1391 code on Chrysler, Dodge, and Jeep vehicles indicates that the PCM has detected an intermittent disagreement between the camshaft position (CMP) sensor and crankshaft position (CKP) sensor signals. These two sensors work together to tell the PCM exactly where each piston is in its cycle so it can fire the spark plugs and fuel injectors at precisely the right moment. When one or both signals become intermittent, the PCM loses its ability to accurately time engine events.
Unlike a complete sensor failure that would trigger a continuous code, the 'intermittent' nature of P1391 means the problem comes and goes. You might notice the engine runs fine sometimes and then suddenly misfires, stalls, or is hard to start. The symptoms often worsen as the engine heats up because heat-related sensor failures are a common pattern with CKP and CMP sensors. Many mechanics recommend replacing both sensors together since they are relatively inexpensive and the labor overlaps.
Address this code within the next week. While the intermittent stalling may be infrequent now, it tends to get worse over time and could leave you stranded. Before replacing sensors, inspect the wiring and connectors for obvious damage. Also check the timing belt or chain — if it has jumped a tooth, new sensors won't fix the underlying timing issue. Both sensors are typically accessible DIY repairs, with the CKP sensor usually located near the transmission bellhousing and the CMP sensor on or near the cylinder head.
Severity
Symptoms
- •Engine misfires or runs rough intermittently
- •Engine stalls unexpectedly, especially at idle
- •Difficulty starting — may require multiple cranking attempts
- •Check engine light illuminated or flashing
- •Noticeable loss of power or hesitation during acceleration
Likely Causes
The CKP sensor generates a signal as the toothed reluctor ring rotates. Internal component degradation causes intermittent signal dropouts, especially when the sensor heats up, leading to timing errors and misfires.
The CMP sensor tells the PCM which cylinder is on its compression stroke. An intermittent signal causes the PCM to lose cylinder synchronization, resulting in mistimed fuel injection and misfires.
If the timing belt or chain has stretched or jumped a tooth, the physical relationship between the crankshaft and camshaft no longer matches the PCM's expectations, triggering this intermittent disagreement code.
Corroded connectors, damaged wire insulation, or loose connections at either sensor cause intermittent signal loss. Heat cycles and vibration worsen these connections over time.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the crankshaft position (CKP) sensor
- Replace the camshaft position (CMP) sensor
- Inspect and repair wiring and connectors to both sensors
- Check timing belt/chain condition and replace if worn or jumped