Distributor index / Cam Sensor Synchronization.
P1391 - Intermittent Loss of CMP or CKP Signal. Loss of the Cam Position Sensor or Crank Position sensor signal has occurred.
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P1391 – Possible symptoms:
(1) random misfire/stumble/bucking/stalling, often over bumps or right hand turns or when going into reverse.
(2) shorted out the Fuel pump/ECU power wire.
Possible causes
- Faulty Camshaft Position (CMP) Sensor
- Camshaft Position (CMP) Sensor harness is open or shorted
- Camshaft Position (CMP) Sensor circuit poor electrical connection.
-CMP SENSOR OUT OF SYNC
-DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)
-DAMAGED TONE WHEEL/PULSE RING (CAMSHAFT)
-IRREGULAR LAB SCOPE PATTERN OF CMP SIGNAL
-INTERMITTENT CKP SIGNAL LOSS WHEN WIRING IS WIGGLED
-IRREGULAR LAB SCOPE PATTERN OF CKP SIGNAL
-WIRING HARNESS INTERMITTENT
-INTERMITTENT CMP SIGNAL LOSS WHEN WIRING IS WIGGLED
-CRANKSHAFT POSITION SENSOR CONNECTOR/WIRING
-FAULTY CRANKSHAFT POSITION SENSOR
Potential Fixes:
Fix #1:
Inspect your wire harnesses for damaged wires, chafed insulation, or failed wire splices. Use a volts/ohms multi-meter to check the resistance of the ground wire circuits from each sensor. Replace corroded ground wires/connectors and clean ground wire connection points.
Fix #2:*
Timing may off. Re-index the distributor/cam sensor per the FSM instructions, or replace faulty distributor/cam sensor pickup module.
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Google
Scan Tools, O-Scopes and Toothpicks, and read the article.
Read this also :
http://www.jeepforum.com/forum/f19/...352-p0353-crank-cam-sensor-issue-fix-3487474/
A mis-indexed distributor/cam sensor may exhibit surging, light bucking or intermittent engine misfiring. This will most likely occur when the vehicle is at operating temperature and under a light load at approximately 2,000 rpm. The proper indexing procedure must be used as outlined in the service manual.