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Home >> Chevrolet >> 2018 >> Trax Premier, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 10 (Engine Controls And Fuel - 1.4L (LE2) - Diagnostic Information And Procedures (P0325-P2635) And Symptoms) >> Diagnostic Information and Procedures >> DTC P121B or P121C >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2018 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON:
    • MAF Sensor Supply Voltage commanded OFF with a scan tool, the following parameters should display:
      • MAF Sensor Supply Voltage Control Circuit Low Voltage Test Status - OK
      • MAF Sensor Supply Voltage Control Circuit Open Test Status - OK
      • MAF Sensor Supply Voltage Control Circuit High Voltage Test Status - Not Run
    • MAF Sensor Supply Voltage commanded ON with a scan tool, the following parameters should be displayed:
      • MAF Sensor Supply Voltage Control Circuit Low Voltage Test Status - Not Run
      • MAF Sensor Supply Voltage Control Circuit Open Test Status - Not Run
      • MAF Sensor Supply Voltage Control Circuit High Voltage Test Status - OK
    • If malfunction 

      Refer to circuit system testing

    • Go to next step: If OK or Not Run 
  2. Engine running, the following parameters should display:
    • MAF Sensor Supply Voltage Command - ON
    • MAF Sensor Supply Voltage Control Circuit Low Voltage Test Status - Not Run
    • MAF Sensor Supply Voltage Control Circuit Open Test Status - Not Run
    • MAF Sensor Supply Voltage Control Circuit High Voltage Test Status - OK
    • If malfunction 

      Refer to circuit system testing

    • Go to next step: If OK or Not Run 
  3. 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.
  4. 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 
  5. All OK
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