LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 367 (Engine Controls Self-Diagnostics - 3.1L Engine) >> Diagnostic Tests >> DTC P0172: Fuel Trim System Rich >> 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. NOTE: If any DTCs are set, other than P0172, refer to those DTCs before proceeding with this test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Connect scan tool. Start and idle the engine at the normal operating temperature in Closed Loop. Record the Long Term Fuel Trim data. Turn ignition switch to OFF position. Turn ignition switch to RUN position, engine OFF. Review the Freeze Frame/Failure Records and record the displayed data for this DTC. Does the scan tool indicate that the Long Term Fuel Trim is less than 13 percent? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  3. Operate the engine at idle. Observe the HO2S 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  5.
  4. Turn ignition switch to OFF position. Visually and physically inspect the following conditions:
    • Blockage of the MAF sensor inlet screen.
    • Splits or kinks in the vacuum hoses Improper connections of the vacuum hoses.
    • Collapsed or restricted air intake duct.
    • Dirty or restricted air filter.
    • 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 engine OFF. Check the HO2S for proper installation. Ensure that the electrical connectors and the wires are secure and not contacting the exhaust system. Did you find and correct the condition? If yes, go to step  7. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  6. Check for the following conditions:
    • Excessive fuel in the crankcase.
    • Evaporative emissions of the control system. Refer to SERVICE BAY TEST  under DRIVE CYCLES.
    • Proper operations of the fuel pressure regulator. Go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.1L CENTURY, GRAND PRIX & MALIBU article.
    • Proper operation of the injectors. Go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.1L CENTURY, GRAND PRIX & MALIBU article.

    Did you find and correct the condition? If yes, go to next step. If no, diagnose engine mechanical problem. Go to appropriate article in ENGINES.

    7. NOTE: After repairs, use the scan tool FUEL TRIM RESET function to reset the Long Term Fuel Trim.
  7. 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 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 step  2. If no, go to next step.
  8. Using the scan tool, observe the stored information in 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 at this time.
scientia non olet · About LEMON Manuals