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Home >> Cadillac >> 1998 >> Catera >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0501 - Vehicle Speed Signal Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then go to next step.
    NOTE: Support lower control arms to ensure drive axles are in normal horizontal position or drive axles will be damaged.
  2. Turn ignition off. Raise and support drive axles. Start engine. Turn traction control system off, if equipped. With engine idling, place transmission in gear. Using scan tool, monitor vehicle speed. If displayed vehicle speed is greater than zero MPH, see DIAGNOSTIC AIDS. If displayed vehicle speed is zero MPH, go to next step.
  3. Turn ignition off. Disconnect ECM harness connector. Connect test light between battery voltage and vehicle speed signal circuit at ECM harness connector. Turn ignition on, with engine off. Using DVOM set to AC, Hz, 4-volt scale, check voltage between ground and vehicle speed signal circuit at ECM harness connector. If DVOM indicates frequency 100-900 Hz, go to step 5). If DVOM does not indicate frequency 100-900 Hz, go to next step.
  4. Turn ignition off. Disconnect theft deterrent module connector. Check vehicle speed signal circuit for open, short to ground or short to voltage. Repair as necessary. After repairs, go to step 6). If circuit is okay, go to step 7).
  5. Turn ignition off. Reconnect ECM connector. Disconnect theft deterrent module connector. Connect Signal Generator Tester (J-33431-B) between ground and vehicle speed signal circuit at theft deterrent module harness connector. Turn ignition on. Turn tester on. Set tester to generate a VSS signal. Using scan tool, monitor vehicle speed. If displayed vehicle speed is greater than zero MPH, diagnose anti-lock brake system. If displayed vehicle speed is zero MPH, go to step 8).
  6. Repair vehicle speed signal circuit between theft deterrent module harness connector and ECM. After repairs, go to step 10).
  7. Check for poor connections and terminal tension at theft deterrent module harness connector. Repair as necessary. After repairs, go to step 10). If connections and terminals are okay, diagnose theft deterrent system.
  8. Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 10). If connections and terminals are okay, go to next step.
  9. Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
  10. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0501 is set, go to step 2). If DTC P0501 is not set, go to next step.
  11. If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.
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