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HOMESERVICE MANUALSBUICK1998RIVIERAREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODESDIAGNOSTIC TROUBLE CODESDTC P1629 - THEFT DETERRENT CRANK SIGNAL MALFUNCTIONDIAGNOSTIC PROCEDURES
1998 Buick Riviera

Diagnostic Procedures

1998 Buick RivieraSECTION Diagnostic Procedures
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Ensure battery is fully charged. Crank engine. If engine cranks, go to next step. If engine does not crank, diagnose and repair VTD.
  3. Turn ignition off. Disconnect VTD module connector. Turn ignition on. Using a DVOM, check voltage between TDS module harness connector ground and VTD fuel enable circuits. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 6).
  4. Turn ignition off. Reconnect TDS module connector. Turn ignition on. Using DVOM in Hertz (Hz) scale, check frequency between engine ground and VTD fuel enable circuit. If frequency is 40-60 Hz, go to next step. If frequency is not 40-60 Hz, go to step 8).
  5. Turn ignition off. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, see DIAGNOSTIC AIDS. If engine does not start, go to step 7).
  6. Check TDS fuel enable circuit for open, short to ground or short to battery voltage. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
  7. Check TDS fuel enable circuit for faulty connection at PCM connector. Repair as necessary. After repairs, go to step 11). If connection is okay, go to step 9).
  8. Check for faulty connection at TDS module. Repair as necessary. After repairs, go to step 11). If connection is okay, go to step 10).
  9. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 11).
  10. Replace VTD module. After replacing module, go to next step.
  11. Clear DTCs. Turn ignition on and observe VTD FUEL DISABLE scan tool display. If scan tool displays INACTIVE, repair is complete. If scan tool does not display INACTIVE, return to step 2)
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.