LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 72 (Engine Controls Self-Diagnostics) >> Diagnostic Tests >> DTC P1639: 5-VOLT REFERENCEWide Open Throttle (WOT)CIRCUIT >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Montana, 2002 Oldsmobile Silhouette, and 2002 Chevrolet Venture. 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, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC, or within the parameters observed in the Freeze Frame/Failure Records. 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. Did you find and correct the condition? If yes, go to step  17. If no, go to next step.
  4. Turn OFF the ignition. Disconnect the A/C pressure sensor connector. Connect a Digital Multimeter (DMM) between the 5-volt reference and a good ground. Turn the ignition ON, with the engine OFF. Does the voltage measure near 5 V? If yes, go to next step. If no, go to step  6.
  5. Turn OFF the ignition. Reconnect the A/C pressure sensor. Disconnect the Fuel Tank Pressure (FTP) sensor. Connect a DMM between the 5-volt reference at the FTP sensor connector and a good ground. Does the voltage measure near 5 V? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to step  13.
  6. Does the voltage measure more than 5 V? If yes, go to next step. If no, go to step  8.
  7. Turn OFF the ignition. Leave the DMM connected from step  4. Disconnect the PCM. Turn ON the ignition, with the engine OFF. Does the voltage measure 0 V? If yes, go to step  15. If no, go to step  12.
  8. Turn OFF the ignition. Leave the DMM connected from step  4. Disconnect the FTP sensor. Turn ON the ignition, with the engine OFF. Does the voltage measure near 5 V? If yes, go to step  14. If no, go to next step.
    9. NOTE: The ignition must me turned OFF for this test.
  9. Turn OFF the ignition. Using a DMM check for continuity between the 5-volt reference circuit and the low reference circuit at the A/C pressure sensor connector. Does the resistance measure infinity or OL? If yes, go to next step. If no, go to step  11.
  10. Leave the ignition OFF. Using a DMM check for continuity between the 5-volt reference circuit and a good chassis ground. Does the resistance measure infinity or OL? If yes, go to step  15. If no, go to next step.
  11. Repair the circuit for a short to chassis ground or a short to A/C pressure sensor low reference. After repairs, go to step  17.
  12. Locate and repair the short to voltage in the 5-volt reference circuit or the FTP signal circuit. Did you complete the repair? After repairs, go to step  17.
  13. Replace the A/C pressure sensor. After repairs, go to step  17.
  14. Replace the fuel tank pressure FTP sensor. After repairs, go to step  17.
  15. Check the 5-volt reference circuit for an open, for a short to chassis ground, or for a poor connection at the PCM. Did you find a problem? If yes, go to step  17. If no, go to next step.
  16. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  17. Clear the DTCs with a scan tool. 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.
  18. Observe the stored information, Capture Info with a scan tool. 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