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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 231 (HVAC - Automatic) >> Diagnostic Information and Procedures >> DTC B2AFF-B2B01 (L3B, LSY) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF and all vehicle systems OFF, disconnect the connector at the M8 Blower Motor. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 6 and ground.
    • If 10 Ω or greater 

      Repair the open/high resistance on circuit 1450 or the ground connection.

    • Go to next step: If less than 10 Ω 
  3. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 

      Repair the open/high resistance on circuit 5840.

    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Test circuit 5840 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Replace the M8 Blower Motor.
    • Go to next step: If the test lamp illuminates 
  4. Ignition ON.
  5. Test for less than 1 V between the control circuit terminal 2 and ground.
    • If 1 V or greater 
    1. Test circuit 754 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found
    2. Replace the K9 Body Control Module
  6. Ignition OFF. It may take up to 10 min for all vehicle systems to power down.
  7. Test for infinite resistance between the control circuit terminal 2 and ground.
    • If less than infinite resistance 
    1. Test circuit 754 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Replace the K9 Body Control Module
    • Go to next step: If infinite resistance 
    8. NOTE:

    Verify the ignition is OFF before connecting the blower motor or incorrect test results may occur.

  8. Ignition OFF, connect the connector at the M8 Blower Motor. Ignition ON.
  9. While backprobing terminal 2 at the M8 Blower Motor, test for greater than 1 V between control circuit and ground.
    • If 1 V or less 

      Replace the M8 Blower Motor.

    • Go to next step: If greater than 1 V 
  10. Verify the voltage decreases and increases while using the controls to change the blower speed selection.
    • If the voltage does not decrease and increase as the blower speed selection is changed 
    1. Test circuit 754 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found
    2. Replace the K9 Body Control Module
    • Go to next step: If the voltage decreases and increases as the blower speed selection is changed 
  11. Replace the M8 Blower Motor.
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