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Home › Chevrolet › 2000 › Venture Plus › Repair and Diagnosis › Engine Performance › System › Engine Controls Self-Diagnostics › Diagnostic Tests › DTC P0172: Fuel Trim System Rich › Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. If any other DTCs are set, diagnose DTCs as necessary before proceeding. If no other DTCs are set, go to next step.
  3. Start and warm engine to normal operating temperature. Ensure system is in closed loop. Using scan tool, select ENG 1 data list. Observe L.T. FUEL TRIM and S.T. FUEL TRIM. If L.T. FUEL TRIM is about -16 percent and S.T. FUEL TRIM is about -11 percent, go to step  5. If fuel trim is not as specified, go to next step.
  4. Using scan tool, clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until DTC test runs. If scan tool indicates that this DTC failed this ignition, go to next step. If scan tool does not indicate that this DTC failed this ignition, see DIAGNOSTIC AIDS .
  5. Inspect air filter element. Replace as necessary. After repairs, go to step  21. If air filter element is okay, go to next step.
  6. Check for collapsed or restricted air intake duct. Repair as necessary. After repairs, go to step  21. If air duct is okay, go to next step.
  7. Inspect throttle body inlet screen for damage or blockage. Repair as necessary. After repairs, go to step  21. If inlet screen is okay, go to next step.
  8. Start engine and check idle quality. If idle is high or rough, go to next step. If idle is okay, go to step  11.
  9. Allow engine to idle. Using scan tool, observe IDLE AIR CONTROL display. If counts are greater than 100, go to step  11. If counts are not greater than 100, go to next step.
  10. Turn ignition off. Inspect throttle body bore, throttle plate and IAC passages for coking and foreign objects. Repair as necessary. After repairs, go to step  21. If no problem is found, go to next step.
  11. Check Idle Air Control (IAC) valve operation. See appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  21. If IAC valve is functioning properly, go to step  13.
  12. Disconnect vacuum hose from fuel pressure regulator and check hose for presence of fuel. If fuel is present, replace fuel pressure regulator. After repairs, go to step  21. If fuel pressure regulator is okay, go to next step.
  13. Turn ignition on. Monitor TP angle display on scan tool while slowly depressing accelerator pedal. If TP angle display increase steadily from 0-100 percent (wide-open throttle), go to next step. If TP angle display does not increase as specified, go to step  19.
  14. Disconnect MAF sensor harness connector. Start engine and allow it to idle. Ensure system is in closed loop. Using scan tool, observe ST FUEL TRIM and LT FUEL TRIM display. If both values change to about zero percent, go to step  21. If one or both values do not change to about zero percent, go to next step.
  15. Diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article. Repair fuel system as necessary. After repairs, go to step  21. If fuel system is okay, go to next step.
  16. Check fuel evaporation system for proper operation. Ensure canister purge solenoid is functioning properly. See appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  21. If fuel evaporation system is functioning properly, go to next step.
  17. Perform injector balance test. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  21. If no problems were found, go to next step.
  18. Visually and physically inspect HO2S 1 for silicon contamination (White powdery deposits). If contamination is evident, replace sensor. After repairs, go to step  21. If sensor is okay, see DIAGNOSTIC AIDS .
  19. Check TP sensor mounting screws. Tighten or replace mounting screws as necessary. If mounting screws are okay, replace TP sensor. After repairs, go to step  21.
  20. Replace MAF sensor. After replacing sensor, go to next step.
  21. Using scan tool, clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info until this DTC test runs. If scan tool indicates that this DTC failed this ignition, go to step  2. If scan tool does not indicate that this DTC failed this ignition, system is okay.
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