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Home >> Chevrolet >> 2021 >> Trailblazer RS, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 9 (Engine Controls And Fuel - 1.0L (L4B L4F L4G LIJ) Or 1.2L (L4H L4K LIF LIH) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0171 or P0172 >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different variant/trim than selected.
  1. Ignition - On/Vehicle - In Service Mode
  2. Verify there are no DTCs set related to the following component/system:
    • B17 Barometric Pressure Sensor
    • B52 Heated Oxygen Sensor
    • B74 Manifold Absolute Pressure Sensor
    • B75C Multifunction Intake Air Sensor
    • B150 Fuel Tank Pressure Sensor
    • B111 Turbocharger Boost Sensor
    • B198 Fuel Composition Sensor
    • Q12 Evaporative Emission Purge Solenoid Valve
    • Q17 Fuel Injector
    • Q38 Throttle Body
    • Engine Misfire
    • Secondary Air Injection System
    • Go to next step: If a related DTC is not set 
  3. Verify the scan tool parameter: MAP Sensor = The value should be within the range listed in the table: Altitude Versus Barometric Pressure
    • Go to next step: If in the specified range 
  4. Engine - Idling
  5. Disconnect the electrical connector: B75C Multifunction Intake Air Sensor

    Verify the scan tool parameter: Long Term Fuel Trim = The parameter value should not change. - Greater than 20%

    • If the change is 20% or greater 

      Refer to DTC P0101 

    • Go to next step: If the change is less than 20% 
  6. Ignition/Vehicle & All vehicle systems - Off
  7. Connect the electrical connector: B75C Multifunction Intake Air Sensor
  8. Engine - Idling
  9. Verify the scan tool parameter: Long Term Fuel Trim = Less than 10%
    • If 10% or greater 

      Refer to Circuit/System Testing - P0171

    • Go to next step: If less than 10% 
  10. Verify the scan tool parameter: Long Term Fuel Trim = Greater than -10%
    • If -10% or less 

      Refer to Circuit/System Testing - P0172

    • Go to next step: If greater than -10% 
  11. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

    Verify the DTC does not set.

    • If the DTC sets 

      Refer to Circuit/System Testing

    • Go to next step: If the DTC does not set 
  12. All OK.
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