mayub78
NAXJA Forum User
- Location
- El Paso Tx.
The cam and crank sensors should be free of grease, oil, and debris.
P1391 - Intermittent Loss of CMP or CKP Signal. Loss of the Cam Position Sensor or Crank Position sensor signal has occurred.
P1391 – Possible symptoms:
(1) random misfire/stumble/stalling, often over bumps or right turns and when going into reverse.
(2) shorted out the Fuel pump/ECU power wire.
Possible causes
- Faulty CamshaftPosition (CMP) Sensor
- Camshaft Position (CMP) Sensor harness is open or shorted
- Camshaft Position (CMP) Sensor circuit poor electrical connection.
Symptoms:
-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
-SENSOR CONNECTOR/WIRING
-CAMSHAFT POSITION SENSOR
-CKP SENSOR CONNECTOR/WIRING
-CRANKSHAFT POSITION SENSOR
Often replacing the sensor fixes this code, but not necessarily. Therefore it's important to check the following:
• Check that the wiring isn't routed too close to to sharp metal edges, or to hot exhaust parts.
• Visually inspect the wiring at the sensor for any burn marks, discoloration indicative of melting or chafing of insulation
• Visually inspect the cam sensor for damage
• Visually inspect the reluctor wheel inside the alternator. Make sure the magnet is firmly attached.
• If all checks out okay, then replace the sensor.
If you buy any OBD-II engine sensors, make sure to buy genuine Jeep sensors.
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.
Google Scan Tools, O-Scopes and Toothpicks, and read the article.
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 Jeep Service Manual.
Hello every one, I have a 4.0 97 Xj std trans with about 230K miles, and have around three months having problems with codes P0320 and P1391, have done almost all of the above, the only two thing I haven't done is the alternator and timing tests, from there on all has been checked.
Haven't done the alternator because it's practically new, two years since I replaced it. And timing because I recently replaced the distributor withe a new one. Since the old one had a bad seal or bushing and oil was coming in. I'm sure the new ones is correctly installed, but I'm going to double check.
Sincerely I'm frustrated, it's my DD and weekend warrior, so I'm stranded without my Xj working accordingly. HELP is appreciated!!