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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 79 (Engine Controls - Self-Diagnostics - 4.0L) >> Diagnostic Tests >> DTC P0172 & P0175: Fuel Trim System Rich, Bank 1 & 2 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. 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? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: If any other DTCs are set, repair DTCs before continuing with this test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, record long term fuel trim data. Turn ignition off. Turn ignition on. Using scan tool, record Long Term Fuel Trim data. Turn ignition off. Turn ignition on. Using scan tool, review Freeze Frame Records and/or Failure Records and record data. Does the scan tool indicate that the Long Term Fuel Trim is less than -13 percent? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  3. Start engine and allow it to idle. Using scan tool, observe HO2S voltage. Does the scan tool indicate that the values are within 200-800 mV and fluctuating? If yes, go to next step. If no, go to step  5.
  4. Turn ignition off. Check Mass Airflow (MAF) sensor inlet screen for blockage. Check vacuum hoses for splits, kinks and proper routing. Check for collapsed or restricted air intake duct. Check for restricted or dirty air filter. Check for throttle body blockage. Did you find and correct the condition? If yes, go to step  7. If no, go to step  6.
  5. Turn ignition off. Ensure HO2S is installed correctly and wiring harness is not touching exhaust. Did you find and correct the condition? If yes, go to step  7. If no, diagnose fuel system. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
  6. Check for excessive fuel in crankcase. Diagnose evaporative emissions control system. Check fuel pressure regulator for proper operation. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Ensure all fuel injectors are functioning properly. Perform fuel injector balance test. See FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Did you find and correct the condition? If yes, go to next step. If no, check engine mechanical condition and repair as necessary.
  7. After repairs, using scan tool fuel trim reset function, reset long term fuel trim. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the 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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