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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 246 (Engine Controls Self-Diagnostics - 3.1L Engine) >> Diagnostic Tests >> DTC P1635: 5-Volt Reference 1 Circuit (Century & Grand PRIX) >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  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 Test. See CONDITIONS FOR RUNNING TEST . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  3. Turn ignition switch to OFF position. Disconnect Exhaust Gas Recirculation (EGR) valve. Turn ignition switch to RUN position, engine OFF. Command the EGR valve to 100 percent using a scan tool. Measure the voltage from the 5-volt reference circuit of the EGR valve to a good ground using a DMM. Is the voltage 4.8-5.2 volts? If yes, go to step  5. If no, go to next step.
  4. Is the voltage more than 5.2 volts? If yes, go to step  8. If no, go to step  6.
  5. Connect the EGR valve. Disconnect the Manifold Absolute Pressure (MAP) sensor harness connector. Command the EGR valve to 100 percent using a scan tool. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground using a DMM. Is the voltage 4.8-5.2 volts? If yes, go to DIAGNOSTIC AIDS . If no, go to step  10.
  6. Monitor the DMM while disconnecting all other devices connected to the 5-volt reference circuit, one at a time. If the voltage changes when one of the devices is disconnected, replace the component. Did you replace a component? If yes, go to step  12. If no, go to next step.
  7. Turn ignition switch to OFF position. Disconnect the Powertrain Control Module (PCM) harness connectors. Test the 5-volt reference circuits for a short to ground or any sensor low reference circuit. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  8. Turn ignition switch to OFF position. Disconnect the Powertrain Control Module (PCM) harness connectors. Turn ignition switch to RUN position, engine OFF. Test all the 5-volt reference circuits' the MAP sensor signal circuit and on Grand Prix, the FTP sensor signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  12. If no, go to next step.
  9. On all models, check for a short between the EGR 5-volt reference circuit and the EGR solenoid control high circuit. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  10. Replace the EGR valve. After repair, go to step  12.
  11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  12. On all Models, using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate vehicle within Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  13. Using the scan tool, observe the stored information in CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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