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Home >> Jeep >> 2002 >> Wrangler Sahara, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1391: Intermittent Loss Of CMP Or CKP >> Testing

DTC P1391: Intermittent Loss Of CMP Or CKP: Testing

    WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.
  1. Start the engine and run until operating temp is reached (Closed Loop) With the DRBIII® under the Miscellaneous menu, choose the Set Sync Signal function and observe the Actual Sync Setting. Does the Actual Sync Setting read In Range? If yes, go to next step. If no, with the DRBIII®, synchronize the Camshaft and Crankshaft Position Sensors. On the 2.5L, it may be necessary to adjust the distributor to get the Cam and Crank within specification.
  2. Turn the ignition off. With the DRBIII® lab scope probe and the Miller Special Tool (6801), backprobe the CMP Sensor Signal circuit in the CMP harness connector. Start the engine. Observe the lab scope screen. Are there any irregular or missing signals? If yes, go to next step. If no, go to step  6.
  3. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals. Ensure the Crankshaft Position Sensor and the Camshaft Position Sensor are properly installed and the mounting bolt(s) are tight. Refer to any Technical Service Bulletins (TSB) that may apply. Were any of the above conditions present? If yes, repair as necessary. If no, go to next step.
  4. Turn the ignition off. Remove the Camshaft Position Sensor. Inspect the Tone Wheel/Pulse Ring for damage, foreign material, or excessive movement. Were any problems found? If yes, repair or replace the Tone Wheel/Pulse Ring as necessary. If no, go to next step.
  5. There are no possible causes remaining, replace the Camshaft Position Sensor.
  6. Turn the ignition off. With the DRBIII® as a Dual Channel Lab Scope and the Miller Special Tool (6801), backprobe the CMP Sensor Signal circuit in the PCM harness connector and in the CMP harness connector. Start the engine. Observe the lab scope screen. Wiggle the related wire harness and gently tap on the Camshaft Position Sensor. Look for any differences between the Channel 1 and Channel 2 patterns, generated by the CMP Sensor. Does the DRBIII® screen display any missing or irregular patterns? If yes, replace the Camshaft Position Sensor or repair the wiring/connection concern. If no, go to next step.
  7. Turn the ignition off. With the DRBIII® lab scope probe and the Miller Special Tool (6801), backprobe the CKP Sensor Signal circuit in the CKP harness connector. Start the engine. Observe the lab scope screen. Are there any irregular or missing signals? If yes, go to next step. If no, go to step  11.
  8. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals. Ensure the Crankshaft Position Sensor and the Camshaft Position Sensor are properly installed and the mounting bolt(s) are tight. Refer to any Technical Service Bulletins (TSB) that may apply. Were any of the above conditions present? If yes, repair as necessary. If no, go to next step.
  9. Turn the ignition off. Remove the Crankshaft Position Sensor. Inspect the Tone Wheel/Flex Plate slots for damage, foreign material, or excessive movement. Were any problems found? If yes, repair or replace the Tone Wheel/Flex Plate as necessary. If no, go to next step.
  10. There are no possible causes remaining, replace Crankshaft Position Sensor.
    11. WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.
  11. The conditions that set this DTC are not present at this time. The following may help in identifying the intermittent condition. Turn the ignition off. With the DRBIII® as a Dual Channel Lab Scope and the Miller Special Tool (6801), backprobe the CKP Sensor Signal circuit in the PCM harness connector and CKP harness connector. Both of the graphs should be identical. Start the engine. Monitor the DRBIII® lab scope screen, both patterns should be the same. Wiggle the related wire harness and gently tap on the Crankshaft Position Sensor. Look for any differences between Channel 1 and Channel 2 patterns generated by the CKP Sensor. Were any erratic or missing signals noticed? If yes, replace the Crankshaft Position Sensor. If no, test is complete.
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