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Home >> Pontiac >> 1996 >> Trans Sport >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0336 - 24X Reference Signal Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform ON-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, see ENGINE DOES NOT START in BASIC TESTING article.
  3. Using scan tool, clear DTC P0336. Start engine and allow it to idle for one minute. Read DTCs. If DTC P0336 resets, go to next step. If DTC does not reset, go to DIAGNOSTIC AIDS.
  4. Disconnect CMP sensor connector. Connect a test light between battery voltage and PCM harness connector sensor feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
  5. Check 24X CKP sensor and CMP sensor feed circuits for short to ground. If a problem is found, repair as necessary and go to step 15. If no problem is found, go to DIAGNOSTIC AIDS.
  6. Connect a fused jumper wire between PCM harness connector sensor feed circuit and battery voltage. Using a DVOM, check voltage between engine ground and PCM harness connector 24X signal circuit. If voltage is 9-16 volts, leave fused jumper wire connected and go to next step. If voltage is not as specified, go to step 8).
  7. Check voltage between engine ground and PCM harness connector sensor ground circuit. If voltage is 9-16 volts, go to step 13). If voltage is not as specified, go to step 10).
  8. Check for open 24X CKP sensor feed circuit. If open is found, repair as necessary and go to step 15). If no open is found, go to next step.
  9. Check for open or short in 24X CKP sensor signal circuit. If a problem is found, repair as necessary and go to step 15). If no problem is found, go to step 12).
  10. Check for open 24X CKP sensor ground circuit. If open is found, repair as necessary and go to step 15). If no open is found, go to step 12).
  11. Replace CMP sensor and go to step 15).
  12. Replace 24X CKP sensor and go to step 15).
  13. Check for faulty connections at PCM. If a faulty connection is found, repair as necessary and go to step 15). If connections are okay, go to next step.
  14. Replace PCM. Program replacement PCM using required equipment. Go to next step.
  15. Read and record FAIL RECORDS data for DTC P0336. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0336 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0336 FAILED THIS IGN, repair is complete.


  1. Perform On-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, see ENGINE DOES NOT START in BASIC TESTING article.
  3. Using scan tool, clear DTC P0336. Start engine and allow to idle for one minute. Read DTCs. If DTC P0336 resets, go to next step. If DTC does not reset, go to DIAGNOSTIC AIDS.
  4. Disconnect ICM and PCM connectors. Check for open or short to ground in 18X reference circuit between ICM and PCM harness connectors. If a problem is found, repair as necessary and go to step 11). If no problem is found, go to next step.
  5. Reconnect ICM connector. Using DVOM, check voltage on 18X reference circuit at PCM harness connector while cranking engine. If voltage is about 3 volts, go to step 8). If voltage is not as specified, go to next step.
  6. Check for faulty connections at ICM. If a faulty connection is found, repair as necessary and go to step 11). If connections are okay, go to next step.
  7. Replace ICM and go to step 11).
  8. Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or ICM. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness. If a problem is found, repair as necessary and go to step 11). If no problem is found, go to next step.
  9. Check for faulty connections at PCM. If faulty connection is found, repair as necessary and go to step 11). If connections are okay, go to next step.
  10. Replace PCM. Program replacement PCM using required equipment. Go to next step.
  11. Read and record FAIL RECORDS data for DTC P0336. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0336 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0336 FAILED THIS IGN, repair is complete.
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