We hav been trying to figure out this code cause it's very odd... first of all we changed out distributor and new crank sensor and once we put everything back together and set the time it ran great...then that's when we got the check engine light...we scanned it and got the P1391 code so we looked it up....however here the funny thing...jeep runs great starts great no issues what so ever...turns on with no issues...no misfires....nothing... actually once we replaces the distributor jeep ran fantastic...we did a ECU reset and while we cleared the code it pop up once again....we need some help figuring out what this could b...and code is still the same....
Chsoriano50
P1391 INTERMITTENT LOSS OF CMP OR CKP,
Intermittent always compounds the trouble shoot. IDEALLY in shop we would scan check the "SYNC" and graph the CKP and CMP waveforms.
You changed Dist - I gotta ask you did set at TDC #1 compression?
The CKP is suspect - did you use a NEW OEM sensor?
Did old sensor have and physical damage?
Check the connectors at the CMP and CKP, inspect the wires several inches from connector - where most damage is seen. Check for corrosion at connector.
carefully observe RPM as you shake tug wiggle the harnesses to the 2 sensors.
Attachment for info - a signal would be seen missing and shows timing of CMP to CKP - SYNC
Intermittent always compounds the trouble shoot. IDEALLY in shop we would scan check the "SYNC" and graph the CKP and CMP waveforms.
You changed Dist - I gotta ask you did set at TDC #1 compression?
The CKP is suspect - did you use a NEW OEM sensor?
Did old sensor have and physical damage?
Check the connectors at the CMP and CKP, inspect the wires several inches from connector - where most damage is seen. Check for corrosion at connector.
carefully observe RPM as you shake tug wiggle the harnesses to the 2 sensors.
Attachment for info - a signal would be seen missing and shows timing of CMP to CKP - SYNC
Attachments
P1391
P1391 - Intermittent Loss of CMP or CKP Signal. Loss of the Cam Position Sensor or Crank Position Sensor signal has occurred.
P1391 JEEP Possible Causes
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.
(3) A improperly 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.
Often replacing the faulty sensor fixes the P1391 code, but not necessarily. Therefore it's important to check the following:
• Check that the Cam and Crank sensor wiring isn't routed too close to sharp metal edges, or to hot exhaust parts.
• Visually inspect the wiring at the sensor for any burn marks, bare wires, or discoloration indicative of melting / chafing of insulation
• Visually inspect the cam sensor for damage. Make sure the magnet is firmly attached. The sensor can be tested.
• Visually inspect the reluctor wheel inside the distributor or Cam Sensor.
• If everything checks out okay, then test the Crankshaft Position Sensor.
If you buy any OBD-II engine sensors, make sure to buy genuine Jeep sensors.
Potential Fixes:
Fix #1:
Inspect your O2 wire harnesses for bent or pushed back wire plugs pins, 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:
The timing may off. Re-index the distributor/cam sensor per the FSM instructions, or replace faulty distributor/cam sensor pickup module.
Read this article: Scan Tools, O-Scopes and Toothpicks here >> Wayback Machine
Read this thread >> Jeep 4.0L P1391, potentially with p0351, p0352, p0353...
Testing the Throttle Position Sensor and Coolant Temperature Sensor is also a good idea.
P1391 - Intermittent Loss of CMP or CKP Signal. Loss of the Cam Position Sensor or Crank Position Sensor signal has occurred.
P1391 JEEP Possible Causes
- Faulty Crankshaft Position Sensor (CKP)
- Crankshaft Position Sensor (CKP) wire harness is open or shorted
- Crankshaft Position Sensor (CKP) wire circuit poor electrical connection
- Faulty Camshaft Position (CMP) Sensor
- Camshaft Position (CMP) Sensor wire harness is open or shorted
- Camshaft Position (CMP) Sensor wire circuit poor electrical connection.
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.
(3) A improperly 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.
Often replacing the faulty sensor fixes the P1391 code, but not necessarily. Therefore it's important to check the following:
• Check that the Cam and Crank sensor wiring isn't routed too close to sharp metal edges, or to hot exhaust parts.
• Visually inspect the wiring at the sensor for any burn marks, bare wires, or discoloration indicative of melting / chafing of insulation
• Visually inspect the cam sensor for damage. Make sure the magnet is firmly attached. The sensor can be tested.
• Visually inspect the reluctor wheel inside the distributor or Cam Sensor.
• If everything checks out okay, then test the Crankshaft Position Sensor.
If you buy any OBD-II engine sensors, make sure to buy genuine Jeep sensors.
Potential Fixes:
Fix #1:
Inspect your O2 wire harnesses for bent or pushed back wire plugs pins, 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:
The timing may off. Re-index the distributor/cam sensor per the FSM instructions, or replace faulty distributor/cam sensor pickup module.
Read this article: Scan Tools, O-Scopes and Toothpicks here >> Wayback Machine
Read this thread >> Jeep 4.0L P1391, potentially with p0351, p0352, p0353...
Testing the Throttle Position Sensor and Coolant Temperature Sensor is also a good idea.
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