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DTC P1391: Intermittent Loss Of CMP Or CKP (2.4L): Testing

  1. Turn ignition on. Using scan tool, read DTCs. If Good Trip counter is displayed for DTC P1391 and displayed count is "0", go to next step. If Good Trip counter for DTC P1391 is not displayed or displayed count is not "0", go to step  10.
  2. Turn ignition off. Note location of CMP sensor located on rear of cylinder head, just below valve cover. Using oscilloscope's voltage lead, backprobe Dark Blue/Gray wire at CMP sensor harness connector. Start engine and observe oscilloscope pattern. If CMP sensor signal pattern is not consistent, go to next step. If CMP sensor signal pattern is consistent, go to step  6.
  3. Turn engine off. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. Visually inspect connectors for corroded, damaged, pushed-out or miswired terminals. Repair connectors as necessary. Ensure CMP sensor mounting bolt is tightened to 115 INCH lbs. (13.0 N.m). Check for any technical service bulletins that may apply and repair as necessary. If no problems are found, go to next step.
  4. Remove CMP sensor. Inspect target magnet and locating dowels for damage or misalignment. If target magnet and locating dowels are okay, go to next step. If target magnet or locating dowels are damaged or misaligned, replace components as necessary.
  5. At this time, CMP sensor is assumed to be defective. Replace CMP sensor.
  6. Turn ignition off. Using oscilloscope's voltage lead, backprobe Brown/Light Blue wire at CKP sensor harness connector. CKP sensor is located on cylinder block, near oil filter. Start engine and observe oscilloscope pattern. If CKP sensor signal pattern is not consistent, go to next step. If CKP sensor signal pattern is consistent, go to step  10.
  7. Turn engine off. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. Visually inspect connectors for corroded, damaged, pushed-out or miswired terminals. Repair connectors as necessary. Ensure CKP sensor mounting bolt is tightened to 115 INCH lbs. (13.0 N.m). Check for any technical service bulletins that may apply and repair as necessary. If no problems are found, go to next step.
  8. Remove CKP sensor. Inspect notches on crankshaft for damage or debris. Crankshaft contains 2 sets of notches ground into the No. 2 counterweight on the crankshaft. If notches on crankshaft are okay and no debris exist, go to next step. If notches on crankshaft are damaged or debris exist, repair or replace crankshaft as necessary.
  9. At this time, CKP sensor is assumed to be defective. Replace CKP sensor.
  10. Turn ignition off. Using oscilloscope's voltage lead, backprobe terminal No. 32 (Brown/Light Blue wire) at PCM C1 connector. PCM is located in left side of engine compartment, in front of battery. Turn ignition on, with engine off. Monitor oscilloscope pattern. No pulses should be generated by CKP sensor. If no pulses are generated, go to next step. If any pulses are generated, replace CKP sensor.
  11. Turn ignition off. Using oscilloscope's voltage lead, backprobe terminal No. 33 (Dark Blue/Gray wire) at PCM C1 connector. Turn ignition on, with engine off. Monitor oscilloscope pattern. No pulses should be generated by CMP sensor. If no pulses are generated, go to next step. If any pulses are generated, replace CMP sensor.
  12. Turn ignition off. Using oscilloscope's voltage lead, backprobe terminal No. 32 (Brown/Light Blue wire) at PCM C1 connector. Start engine. While monitoring oscilloscope pattern, wiggle CKP sensor signal circuit from CKP sensor to PCM. If CKP sensor signal pattern is consistent, go to next step. If CKP sensor signal pattern is not consistent, repair wiring harness where wiggling caused oscilloscope pattern to become inconsistent.
  13. Turn ignition off. Using oscilloscope's voltage lead, backprobe terminal No. 33 (Dark Blue/Gray wire) at PCM C1 connector. Start engine. While monitoring oscilloscope pattern, wiggle CMP sensor signal circuit from CMP sensor to PCM. If CMP sensor signal pattern is consistent, go to next step. If CMP sensor signal pattern is not consistent, repair wiring harness where wiggling caused oscilloscope pattern to become inconsistent. If wiring harness is okay, replace CMP sensor.
  14. At this time, conditions for DTC to set do not exist or fault is an intermittent problem. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, monitor parameters related to DTC while wiggling connectors and wiring harness. If value changes while wiggling connectors and wiring harness, repair connectors and wiring harness where wiggling caused value to change. If value does not change, review Freeze Frame data using scan tool. Attempt to duplicate condition that caused DTC to set. Check for any related technical service bulletins that may apply. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. See WIRING DIAGRAMS article. If no problems are indicated, test is complete.
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