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P.1391 error code
- Thread starter Jimbo97
- Start date
4x4JeePmaNthINg
NAXJA Forum User
- Location
- Colorado
that code is pure evil. replace the crank position sensor to, then if that doesnt work, down the rabbit hole you go.
- Location
- Minneapolis, MN
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/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, Faulty Crankshaft Position Sensor (CPS/CKP)
- Camshaft Position (CMP) Sensor or Crankshaft Position Sensor (CPS/CKP) wire harness is open or shorted
- Camshaft Position (CMP) Sensor or Crankshaft Position Sensor (CPS/CKP) 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
-CMP SENSOR CONNECTOR/WIRING
-FAULTY CAMSHAFT 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 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. The sensor can be tested.
• 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 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.
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.
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, Faulty Crankshaft Position Sensor (CPS/CKP)
- Camshaft Position (CMP) Sensor or Crankshaft Position Sensor (CPS/CKP) wire harness is open or shorted
- Camshaft Position (CMP) Sensor or Crankshaft Position Sensor (CPS/CKP) 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
-CMP SENSOR CONNECTOR/WIRING
-FAULTY CAMSHAFT 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 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. The sensor can be tested.
• 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 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.
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.
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