LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 116 (Engine Controls - Self-Diagnostics - 4.0L) >> Diagnostic Tests >> DTC P1635: 5-Volt Reference 1 Circuit >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Observe the Freeze Frame/Failure Records data for this DTC. Turn the ignition OFF for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  3. Visually and physically inspect the PCM and engine grounds. Ensure that the grounds are clean and secure. If a problem is found, repair as necessary. Was a problem found? If yes, go to step  13. If no, go to next step.
  4. Turn OFF the ignition. Disconnect the EGR valve electrical connector. Turn the ignition ON, with the engine OFF. Using a DMM, measure voltage between the 5-volt reference circuit and engine ground. Is voltage near 5 V? If yes, go to step  6. If no, go to next step.
  5. Is voltage more than 5 V? If yes, go to step  9. If no, go to step  7.
  6. Reconnect EGR Valve. Disconnect throttle position sensor. Using a DMM, measure voltage between the 5-volt reference 1 circuit and engine ground. Is voltage near 5 V? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to step  10.
  7. Monitor DMM while disconnecting all other devices connected to the 5-volt reference circuit one at a time. If voltage changes when one of the above components are disconnected, replace the component. Was a component replaced? If yes, go to step  13. If no, go to next step.
  8. Turn the ignition OFF. Disconnect the PCM. Check the 5-volt reference circuit for a short to ground or any sensor low reference circuit. If a problem is found, repair as necessary. Was a problem found? If yes, go to step  13. If no, go to step  12.
  9. Turn OFF the ignition. Disconnect the PCM. Turn the ignition ON, with the engine OFF. Check the following circuits for a short to voltage:
    • The 5-volt reference circuit.
    • The manifold absolute pressure MAP sensor signal circuit.

    If a problem is found, repair as necessary. Was a problem found? If yes, go to step  13. If no, go to step  12.

  10. Check for a short between the EGR control high circuit and the 5-volt reference circuit and repair as necessary. Did you find and correct a condition? If yes, go to step  13. If no, go to next step.
  11. Replace the EGR valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  13.
  12. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  13. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  14. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
scientia non olet · About LEMON Manuals