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Home >> Pontiac >> 2003 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0172: Fuel Trim System Rich >> 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. NOTE: If any DTCs are set, other than P0172, refer to those DTCs before continuing. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Install scan tool. Start and idle the engine at the normal operating temperature in Closed Loop. Record the long term fuel trim data. Turn OFF the engine. Turn ON ignition, with the engine OFF. Review the Freeze Frame/Failure Records and record displayed data for this DTC. Does the scan tool indicate that the Fuel Trim Index is less than -13%? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  3. Operate the engine at idle. Observe O2S parameters with a scan tool. Does the scan tool indicate that the values are 200-800 mV and fluctuating? If yes, go to next step. If no, go to step  5.
  4. Turn OFF the engine. Visually and physically inspect the following items:
    • The inlet screen of the Mass Airflow (MAF) sensor for blockage.
    • Vacuum hoses for splits, kinks, and proper connections.
    • The air intake duct for being collapsed or restricted.
    • The air filter for being dirty or restricted.
    • Check for objects blocking the throttle body.

    Did you find and correct the condition? If yes, go to step  7. If no, go to step  6.

  5. Turn OFF the engine. Inspect the HO2S for proper installation. Ensure electrical connectors and wires are secured and not contacting the exhaust system. Did you find and correct the condition? If yes, go to step  7. If no, diagnose fuel system. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L AZTEK & RENDEZVOUS article.
  6. Inspect for the following conditions:
    • Excessive fuel in the crankcase.
    • Evaporative emissions control system.
    • Fuel pressure regulator for proper operation.
    • Ensure that all injectors are functioning properly.
    • Perform the Fuel Injector Balance Test.

    Did you find and correct the condition? If yes, go to next step. If no, see appropriate article in ENGINES.

    7. NOTE: After any of the above repairs, use scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.
  7. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the 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.
  8. 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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