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Home >> Buick >> 1996 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - 3.1L >> Diagnostic Trouble Codes >> DTC P1374 - 3X Reference Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to NO START DIAGNOSIS (A-3) in BASIC TESTING article.
  3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1374 until DTC P1374 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Ignition off. Unplug ICM 14-way connector. Install an injector test light at any injector harness connector. With test light connected to ground, repeatedly touch test light to 3X reference (high) circuit terminal at ICM harness connector. If test light flashes, go to step 8). If test light does not flash, go to next step.
  5. Turn ignition off. Disconnect PCM connector. Check 3X reference circuit for an open or short circuit. Repair as necessary. After repair is completed, go to step 11) If circuit is okay, go to next step.
  6. Check 3X reference circuit for poor terminal connection at PCM connector. Repair as necessary. After repair is completed, go to step 11) If connection is okay, go to next step.
  7. Check ICM wiring harness routing. Ensure harness is not close to high voltage components. Check if ignition coil is arcing to wiring harness or ICM. Repair as necessary. After repair is completed, go to step 11). If no problems are found, go to step 10).
  8. Check for poor terminal connections at ICM connector. Repair as necessary. After repair is completed, go to step 11). If no problems are found, go to next step.
  9. Replace ICM. After repair is completed, go to step 11).
  10. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to next step.
  11. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1374 until DTC P1374 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.
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