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DTC P1391: Intermittent Loss Of CMP Or CKP: Testing

NOTE: CMP or CKP sensor signal loss can be detected by an RPM change, DTC or by observing oscilloscope pattern. Refer to manufacturer's operation manual for instructions in use of oscilloscope and procedure for pattern analysis.
  1. Turn ignition on. Using scan tool, read DTCs. If GLOBAL GOOD TRIP counter is not displayed or displayed count is not "0", go to step  13. If GLOBAL GOOD TRIP counter is displayed and displayed count is "0", go to next step.
  2. Turn ignition off. Ensure CMP sensor connector is connected. On 2.7L, CMP sensor is mounted in front of timing cover. On 3.2L and 3.5L, CMP sensor is mounted in timing belt cover, above left camshaft sprocket. On all models, using oscilloscope's voltage lead, backprobe terminal No. 3 (Tan/Yellow wire) at CMP sensor harness connector. See Figure. 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 and/or CKP sensor mounting bolts are tight. Check for any technical service bulletins that may apply. If no problems are found, go to next step.
  4. Ensure ignition is off. Remove CMP sensor. Inspect tone wheel/pulse ring for damage or looseness. Repair or replace tone wheel/pulse ring as necessary. If tone wheel/pulse ring is okay, go to next step.
  5. At this time, CMP sensor is assumed to be defective. Replace CMP sensor.
  6. Turn ignition off. Ensure CKP sensor connector is still connected. Disconnect CKP sensor connector. CKP sensor is mounted to passenger side of transaxle housing, above the differential housing. See Figure. Using oscilloscope's voltage lead, backprobe Gray/Black wire at CKP sensor connector. 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 CMP sensor and/or CKP sensor mounting bolts are tight. Check for any technical service bulletins that may apply. If no problems are found, go to next step.
  8. Remove CKP sensor. Inspect tone wheel/flexplate for damage, foreign material or excessive movement. Repair or replace tone wheel/flexplate as necessary. If tone wheel/flexplate is okay, go to next step.
  9. At this time, CKP sensor is assumed to be defective. Replace CKP sensor.
  10. 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 and/or CKP sensor mounting bolts are tight. Check for any technical service bulletins that may apply. If no problems are found, go to next step.
  11. Turn ignition off. Using oscilloscope's voltage lead, backprobe terminal No. 33 (Tan/Yellow wire) at PCM C1 harness connector. See Figure. PCM is located on left side of engine compartment, between Power Distribution Center (PDC) and Transmission Control Module (TCM). See Figure. Start engine. While monitoring oscilloscope pattern, wiggle wiring harness from CMP sensor to PCM. If CMP sensor signal pattern remains consistent while wiggling wiring harness, go to next step. If CMP sensor signal pattern does not remain consistent while wiggling wiring harness, repair wiring harness where wiggling caused CMP sensor signal pattern to become inconsistent.
  12. Turn ignition off. Using oscilloscope's voltage lead, backprobe terminal No. 32 (Gray/Black wire) at PCM C1 harness connector. Start engine. While monitoring oscilloscope pattern, wiggle CKP sensor signal circuit from CKP sensor to PCM. If CKP sensor signal pattern is consistent, no problem is indicated at this time. Test is complete. 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 (Tan/Yellow wire) at PCM C1 harness connector. See Figure. PCM is located on left side of engine compartment, between Power Distribution Center (PDC) and Transmission Control Module (TCM). See Figure. 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, check wiring harness where wiggling caused oscilloscope pattern to become inconsistent. Repair wiring as necessary. If wiring harness is okay, replace CMP sensor.
  14. 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 and/or CKP sensor mounting bolts are tight. Check for any technical service bulletins that may apply. If no problems are found, go to next step.
  15. Using oscilloscope's voltage lead, backprobe terminal No. 32 (Gray/Black wire) at PCM C1 harness connector. Start engine. While monitoring oscilloscope pattern, wiggle wiring harness from CKP sensor to PCM. If CKP sensor signal pattern remains consistent while wiggling wiring harness, no problem is indicated at this time. Test is complete. If CKP sensor signal pattern does not remain consistent while wiggling wiring harness, check wiring harness where wiggling caused CKP sensor signal pattern to become inconsistent. Repair wiring as necessary. If wiring harness is okay, replace CKP sensor.
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