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Home >> Chevrolet >> 2007 >> Optra5 LS, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls And Fuel - 1.8L (L79) >> Diagnostic Information and Procedures >> DTC P0171 or P0172 >> Circuit/System Testing

Circuit/System Testing

  1. Verify that none of the following conditions exist:
    • Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Splits, kinks, or improper connections at the vacuum hoses
    • The fuel system is operating lean or rich. Refer to Fuel System Diagnosis .
    • The fuel injectors are operating lean or rich. Refer to Fuel Injector Solenoid Coil Test .
    • Missing, restricted, or leaking exhaust components-Refer to Symptoms - Engine Exhaust .
    • Vacuum leaks at the intake manifold, throttle body, and injector O-rings - P0171
    • Leaking crankcase ventilation system - P0171
    • The air intake duct for being collapsed or restricted possibly by a restricted air filter- P0172
    • Leaking fuel pressure regulator-Inspect for evidence of fuel in the vacuum line. Refer to Fuel System Diagnosis  - P0172.
    • Excessive fuel in the crankcase - P0172
    • The incorrect operation of the evaporative emissions control system - P0172
  2. If all conditions test normal, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .
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