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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 325 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> DTC B0208: Rear Blower Motor Speed >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 GMC Acadia. 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 X1 harness connector at the K8A Blower Motor Control Module - Auxiliary. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 5 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminal 6 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF, remove the test lamp.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF, remove the test lamp.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary and disconnect the harness connector at the M8B Blower Motor - Auxiliary.
    4. Test for infinite resistance between the M8B Blower Motor - Auxiliary B+ circuit terminal B and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the M8B Blower Motor - Auxiliary.
    • If the test lamp illuminates 
  5. Remove the test lamp.
  6. Ignition ON. Test for less than 1 V between the control circuit terminal 3 and ground.
    • If 1 V or greater 
    1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module. Ignition ON.
    2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K33 HVAC Control Module
    • If less than 1 V 
  7. Ignition OFF. It may take up to 2 min for all vehicle systems to power down.
  8. Test for infinite resistance between the control circuit terminal 3 and ground.
    • If less than infinite resistance 
    1. Disconnect the X2 harness connector at the K33 HVAC Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K33 HVAC Control Module
    • If infinite resistance 
  9. Ignition OFF, connect the X1 harness connector at the K8A Blower Motor Control Module - Auxiliary. Ignition ON.
  10. While backprobing terminal 31 X1 at the K8A Blower Motor Control Module - Auxiliary, test for greater than 1 V between control circuit and ground.
    • If less than 1 V 

      Replace the K8A Blower Motor Control Module - Auxiliary.

    • If 1 V or greater 
  11. Verify the voltage decreases and increases while using the controls to change the rear blower speed selection.
    • If the voltage does not decrease and increase as the blower speed selection is changed 
    1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module.
    2. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K33 HVAC Control Module.
    • If the voltage decreases and increases as the blower speed selection is changed 
  12. Ignition OFF, disconnect the harness connector at the M8B Blower Motor - Auxiliary, ignition ON and blower ON.
  13. Verify a test lamp illuminates between the B+ terminal B and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω replace the K8A Blower Motor Control Module - Auxiliary.
    • If the test lamp illuminates 
  14. Ignition OFF, connect the harness connector at the M8B Blower Motor - Auxiliary. Ignition ON.
  15. While backprobing terminal 2 X2 at the K8A Blower Motor Control Module - Auxiliary, test for greater than 1 V between control circuit and ground.
    • If less than 1 V 
    1. Ignition OFF, disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary and the harness connector at the M8B Blower Motor - Auxiliary.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the M8B Blower Motor - Auxiliary.
    • If 1 V or greater 
  16. Verify the voltage decreases and increases while using the controls to change the rear blower speed selection.
    • If the voltage does not decrease and increase as the blower speed selection is changed 

      Replace the K8A Blower Motor Control Module - Auxiliary.

    • If the voltage decreases and increases as the blower speed selection is changed 
  17. Test or replace the M8B Blower Motor - Auxiliary.
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