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Home >> Cadillac >> 1996 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1642 - Vehicle Speed Output Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on. Using scan tool, select ENGINE 3 mode and note VEHICLE SPEED DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 5).
  3. Raise and support drive wheels. Start engine. Spin wheels for about 2 seconds to generate a vehicle speed signal. In DTC INFO mode, select FAIL THIS IGN on scan tool. If scan tool indicates that DTC failed in this ignition cycle, go to next step. If scan tool does not indicate that DTC failed in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
  4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and vehicle speed output signal circuit at PCM harness connector C2 terminal. If voltage reading is 10 volts or greater, go to step 7). If voltage reading is less than 10 volts, go to next step.
  5. Repair open or short in vehicle speed output circuit between PCM and IPC, and cruise control module and RAC module. Repair as necessary.
  6. Repair short to voltage in vehicle speed output circuit between PCM and IPC, and cruise control module and RAC module. Repair as necessary.
  7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
  8. Replace PCM. Program replacement PCM using required equipment.
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