The P1391 code on your 2021 Chrysler 300 indicates the PCM is not receiving a signal from the crankshaft position sensor. This Stellantis-specific code critically affects your 300's 3.6L Pentastar V6 or 5.7L HEMI V8 engine's ability to start and run, as the crankshaft position signal is essential for ignition timing and fuel injection.
Understanding P1391 on Chrysler 300
The crankshaft position (CKP) sensor monitors crankshaft rotation and provides reference pulses to the PCM. This signal is required to determine engine position for precise ignition timing and fuel injection events. Code P1391 sets when the PCM receives no signal from the CKP sensor during cranking or running, which typically prevents the engine from starting.
Common Symptoms
- Engine cranks but won't start
- Check engine light on
- Engine stalls and won't restart
- Intermittent no-start condition
- Engine cuts out while driving
- Rough running if signal is intermittent
Primary Causes
- Failed crankshaft position sensor
- Damaged CKP sensor wiring
- Corroded sensor connector
- Excessive sensor to reluctor gap
- Damaged reluctor ring on crankshaft
- PCM input circuit failure
- Wiring harness damage from heat or oil
Diagnostic Procedure for 2021 Chrysler 300
First, verify the CKP sensor is producing a signal during cranking using an oscilloscope or scan tool that displays CKP RPM. Inspect the CKP sensor and connector for damage, corrosion, or oil contamination. Test sensor resistance (typically 200-1000 ohms depending on type). Check wiring continuity between sensor and PCM. Inspect reluctor ring for damage if accessible. Verify proper sensor air gap.
Repair Solutions
Replace faulty CKP sensor - this is the most common cause. Clean and repair corroded connectors, applying dielectric grease to prevent recurrence. Repair damaged wiring with proper splicing techniques, ensuring heat-resistant materials near exhaust components. If reluctor ring is damaged, more extensive engine work may be required. Clear codes and verify proper signal during cranking and running.