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Home >> Chevrolet >> 1998 >> Tracker 4D Utility, RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0171: Fuel Trim System Lean >> Diagnostic Test

Diagnostic Test

  1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK  .
  2. Connect scan tool to data link connector. Start engine. Operate vehicle while loop status indicates CLOSED LOOP. Observe short term fuel trim parameter on scan tool. If 0-20 percent is displayed, go to next step. If 0-20 percent is not displayed, go to step 4).
  3. Turn ignition switch to RUN position. Clear scan tool information. Operate vehicle within freeze frame conditions. Observe total fuel trim parameter. If 0-43 percent is not displayed, go to next step. If 0-43 percent is display, check the following and repair as necessary:
    • Vacuum leaks.
    • Exhaust leaks.
    • Fuel pressure while driving vehicle under different conditions. If fuel pressure is to low, system can go lean setting DTC P0171.
    • Fuel contamination.
    • Mass airflow sensor.
    • Component connections.
    • Heated oxygen sensors.
    • Damaged wiring harness.
  4. Visually and physically check the following items: PCV valve for proper installation, exhaust system for leaks, EGR for proper operation, component connectors for proper contact and sensors for proper installation. If problems do not exist, go to next step. If problem(s) exists, go to step 10).
  5. Turn ignition switch to LOCK position. Relieve fuel pressure. See FUEL SYSTEM in BASIC TESTING article. Install fuel pressure gauge. Start engine. Observe fuel pressure at an idle. If fuel pressure is 30-37 psi (2.1-2.6 kg/cm2 ), go to next step. If fuel pressure is not 30-37 psi (2.1-2.6 kg/cm2 ), repair fuel system as necessary.
  6. Check fuel system for excessive water, alcohol or other contaminates. If the fuel is contaminated, go to next step. If the fuel is not contaminated, go to step 8).
  7. Replace contaminated fuel and go to step 10).
  8. Check fuel injector for restrictions. If fuel injectors are not restricted, go to next step. If fuel injector are restricted, repair as necessary and go to step 10).
    NOTE: Before replacing HO2S (sensor 1), inspect sensor for contamination. If contamination is present, determine cause and repair before installing new HO2S (sensor 1).
  9. Check HO2S (sensor 1) for contamination. If HO2S (sensor 1) is contaminated, replace as necessary and go to next step. If HO2S (sensor 1) is not contaminated, repair by symptom. See TESTS W/O CODES article.
  10. Test drive vehicle under conditions that set the DTC. Check for other DTCs. If DTCs were retrieved, perform appropriate DTC test. If no DTCs were retrieved, system is okay at this time.
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