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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 26 (Engine Controls Self-Diagnostics - 5.0L & 5.7L) >> Diagnostic Tests >> DTC P1635: 5-Volt Reference 1 Circuit >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2001 GMC Savana, 2001 Chevrolet RV Cutaway, 2001 Chevrolet Cutaway, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK . After performing powertrain diagnostic system check, go to next step.
  2. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, see INTERMITTENT TROUBLE CODE DETERMINATION  under ON-BOARD DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
  3. Visually and physically inspect PCM and engine grounds. Ensure grounds are clean and secure. If problem was found, repair as necessary. After repairs, go to step  13. If problem was not found, go to next step.
  4. Turn ignition off. Disconnect EGR valve connector. See COMPONENT LOCATIONS . Turn ignition on, engine off. Using a DVOM, measure voltage between EGR valve connector terminal "D" (Gray wire) and ground. See Figure. If voltage is about 5 volts, go to step  6. If voltage is not about 5 volts, go to next step.
  5. If voltage is more than 5 volts, go to step  9. If voltage is not more than 5 volts, go to step  7.
  6. Reconnect EGR Valve. Disconnect TP sensor. Using a DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire) and ground. See Figure. If voltage is about 5 volts, see INTERMITTENT TROUBLE CODE DETERMINATION  under ON-BOARD DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM. If voltage is not about 5 volts, go to step  10.
  7. Monitor DVOM while disconnecting all other devices connected to 5-volt reference circuit one at a time. If voltage changes when one of these components is disconnected, replace component. If problem was found, repair as necessary. After repairs, go to step  13. If problem was not found, go to next step.
  8. Turn ignition off. Disconnect PCM. Check Gray wire for short to ground or any sensor low reference circuit. If problem was found, repair as necessary. After repairs, go to step  13. If problem was not found, go to step  12.
  9. Turn ignition off. Disconnect PCM. Turn ignition on, engine off. Check Gray wire and Light Green wire between MAP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step  13. If problem was not found, go to step  12.
  10. Check for short between Gray wire and Red wire between EGR valve and PCM. If problem was found, repair as necessary. After repairs, go to step  13. If problem was not found, go to next step.
  11. Replace EGR valve. After repairs, go to step  13.
  12. Replace PCM. Program PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step. If DTC does not run and pass, go to step  2.
  14. Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.
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