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Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. 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 (Alternative Fuels). If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS (ALTERNATIVE FUELS)  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: If any DTCs are set other than P0172, diagnose those DTCs before proceeding with this diagnostic. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Install a scan tool. Review the Freeze Frame/Failure Records and record displayed data for this DTC. Select FUEL TRIM DATA parameter. Start the engine and observe the FUEL TRIM INDEX. Is the fuel trim index parameter less than -46 percent? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  3. Start the engine. Allow the engine to reach operating temperature. Put the transmission in Park (A/T) or Neutral (M/T) position. Turn all accessories OFF. Allow the engine to idle. Observe the Manifold Absolute Pressure (MAP) sensor parameter using a scan tool. Is the MAP sensor parameter 2.76-6.09 psi (19-42 kPa)? If yes, go to next step. If no, go to DTC P0105: MANIFOLD ABSOLUTE PRESSURE SENSOR PERFORMANCE/RANGE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.
  4. Start and operate the engine at idle. Observe O2S parameters using 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  6.
  5. Turn engine OFF. Visually and physically check the following items:
    • Vacuum hoses for splits, kinks, and proper connections.
    • Collapsed or restricted air intake duct.
    • Dirty or restricted air filter.
    • Objects blocking throttle body.

    Did you find and correct the condition? If yes, go to step  8. If no, go to step  7.

  6. Turn ignition switch to OFF position. Check the O2S for proper installation. Ensure electrical connectors and wires are secured and not contacting the exhaust system. Check for continuity between the signal circuit and the low reference circuit. Did you find and correct the condition? If yes, go to step  8. If no, go to FUEL SYSTEM DIAGNOSIS (CNG) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
  7. Check for the following:
    • Excessive fuel in the crankcase.
    • The EVAP system.
    • The gasoline fuel pressure regulator for proper operation.
    • Ensure that all injectors are functioning properly. See FUEL INJECTOR COIL TEST under FUEL SYSTEMS (CNG) in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.

    Did you find and correct the condition? If yes, go to next step. If no, diagnose base engine components for cause of misfire. Go to BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES under SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article.

    8. NOTE: After repair, use the scan tool FUEL TRIM RESET function to reset the Long Term Fuel Trim.
  8. Clear the DTCs using a scan tool. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . 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 step  2. If no, go to next step.
  9. Observe the CAPTURE INFO using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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