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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 129 (Engine Controls And Fuel - 3.6L (LF4) - Diagnostic Information And Procedures (1 Of 3)) >> Diagnostic Information and Procedures >> DTC P0171, P0172, P0174, or P0175 >> Circuit/System Testing

Circuit/System Testing

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P0171, P0174

  1. Ignition/Vehicle - Off
  2. Verify the following conditions do not exist:
    • B75 Mass Airflow Sensor - Contamination of the measuring element/Skewed/Water intrusion
    • Q17 Fuel Injector - Restricted - Refer to: Fuel Injector Diagnosis
    • Air Cleaner Element - Incorrect/ Missing
    • Engine - Vacuum leak
    • Evaporative Emission Canister - Cracked/Leaking/Visible Damage
    • Exhaust System - Leaking/Missing components - Refer to: Symptoms - Engine Exhaust
    • Fuel - Contaminated/Poor Quality - Refer to: Alcohol/Contaminants-in-Fuel Diagnosis
    • Fuel level - Low
    • Fuel Pressure - Low - Refer to: Fuel System Diagnosis
    • Intake Manifold - Vacuum leak
    • Intake Air Duct - Cracked/Leaking/Loose Clamps/Visible Damage
    • Oil Filler Cap - Leaking/Missing
    • Positive Crankcase Ventilation System - Incorrect connection/Leaking/Restricted
    • Vacuum Hoses - Incorrect connection/Kinked/Leaking/Restricted
    • Vacuum leak @ Engine - Oil Level Indicator and Tube /Oil Filler Cap
    • If a condition exists 

      Repair or replace as necessary

    • Go to next step: If no condition exists 
  3. All OK.

P0172, P0175

  1. Ignition/Vehicle - Off
  2. Verify the following conditions do not exist:
    • B75 Mass Airflow Sensor - Contamination of the measuring element
    • Q17 Fuel Injector - Leaking - Refer to: Fuel Injector Diagnosis
    • Q38 Throttle Body - Blocked/Coking/Restricted
    • Air Cleaner Element - Dirty/Restricted/Saturated with water
    • Evaporative Emission Canister - Missing components/Saturated with fuel/Visible Damage
      • NOTE:

      If a condition exists - Replace the component: Engine Oil

    • Excessive fuel in the crankcase - Verify the condition does not exist with the component and repair as necessary:
    • Exhaust System/Catalyst System - Leaking/Missing components/Restricted/Severe discoloration caused by excessive temperatures/Visible Damage - Refer to: Symptoms - Engine Exhaust
    • Fuel - Contaminated/Poor Quality - Refer to: Alcohol/Contaminants-in-Fuel Diagnosis
    • Fuel Pressure - High - Refer to: Fuel System Diagnosis
    • Intake Air Duct - Collapsed/Restricted/Visible Damage
    • If a condition exists 

      Repair or replace as necessary

    • Go to next step: If no condition exists 
  3. All OK.
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