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Home >> Pontiac >> 2003 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P1635: 5-Volt Reference 1 Circuit >> Diagnostic Procedures
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Diagnostic Procedures

  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 ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running DTC or within the parameters observed in the Freeze Frame/Failure Records. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.4L AZTEK & RENDEZVOUS article.
  3. Turn ignition off. Disconnect the EGR valve. Turn ignition on, with engine off. Command the EGR solenoid to 100 percent with a scan tool. Measure the voltage from the 5-volt reference circuit to a good ground with a DVOM. Is the voltage 4.8-5.2 volts? If yes, go to step  5. If no, go to next step.
  4. Is the voltage measured more than 5.2 volts? If yes, go to step  8. If no, go to step  6.
  5. Connect the EGR valve. Disconnect the MAP sensor. Command the EGR solenoid to 100 percent with a scan tool. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DVOM. Is the voltage within 4.8-5.2 volts? If yes, see DIAGNOSTIC AIDS . If no, go to step  11.
  6. Monitor a DVOM while disconnecting all other devices connected to the 5-volt reference circuit, one at a time. If voltage changes when one of the devices are disconnected, replace the affected component (MAP, FTP, TP and TP sensors). Was a component replaced? If yes, go to step  13. If no, go to next step.
  7. Turn ignition off. Disconnect the PCM. Test the 5-volt reference circuit for a short to ground or any sensor low reference circuit. Did you find and correct the condition? If yes, go to step  13. If no, go to step  12.
  8. Monitor the DVOM while disconnecting the MAP sensor and FTP sensor, one at a time. If voltage returns to within 4.8-5.2 volts when one of the devices is disconnected, test that sensors signal circuit for a short to voltage. If yes, go to step  13. If no, go to next step.
  9. Test the 5-volt reference circuits for a short to voltage. Did you find and correct the condition? If yes, go to step  13. If no, go to next step.
  10. Test for a short between the EGR 5-volt reference circuit and the EGR solenoid high control circuit. Did you find and correct the condition? If yes, go to step  13. If no, go to step  12.
  11. Replace EGR valve. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. After repairs, go to step  13.
  12. Replace PCM. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  13. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  14. 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.
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