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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, and 2002 Chevrolet Cavalier. 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. NOTE: If any DTCs are set, other than P0172, refer to those DTCs before proceeding with this diagnosis. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Install scan tool. Review the Freeze Frame/Failure Records and record displayed data for this DTC. Select Fuel Trim Data parameter. Start engine and observe the Fuel Trim Index. Does the scan tool indicate that the fuel trim index is less than -46 percent? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  3. Operate the engine at idle. Observe the oxygen sensor parameters with a scan tool. Does the scan tool indicate that the values are within the specified range of 200-80 millivolts and fluctuating? If yes, go to next step. If no, go to step  5.
  4. Turn engine off and inspect the following: Visually and physically inspect 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 or for objects blocking throttle body. Did you find and correct the condition? If yes, go to step  7. If no, go to step  6.
  5. Turn engine off. 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.
  6. Inspect for excessive fuel in the crankcase. Check evaporative emissions control system and 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, diagnose engine mechanical problem.
    7. NOTE: After repairs, use the 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 the 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. With a scan tool, observe the stored information, Capture Info. 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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