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Home >> Cadillac >> 2018 >> CT6 Plug-In >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC System - Automatic >> Diagnostic Information and Procedures >> DTC B0208 >> Circuit/System Testing

Circuit/System Testing

  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 10 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. 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.
    • Go to next step: 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 terminal 6 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: 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 control 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.
    • Go to next step: If the test lamp illuminates 
  5. Ignition OFF, remove the test lamp and disconnect the X2 harness connector at the K33 HVAC Control Module, ignition ON.
  6. Test for less than 1 V between the K8A Blower Motor Control Module - Auxiliary control circuit terminal 3 X1 and ground.
    • If 1 V or greater 

      Repair the short to voltage on the circuit.

    • Go to next step: If less than 1 V 
  7. Ignition OFF.
  8. Test for infinite resistance between the control circuit and ground.
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  9. 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.

    • Go to next step: If less than 2 Ω 
  10. Connect the harness connectors at the K8A Blower Motor Control Module - Auxiliary and the K33 HVAC Control Module, and disconnect the harness connector at the M8B Blower Motor - Auxiliary, ignition ON and blower ON.
  11. Verify a test lamp illuminates between the B+ circuit 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.
    • Go to next step: If the test lamp illuminates 
  12. Connect a test lamp between the control circuit terminal A and the B+ circuit terminal B.
  13. Verify the test lamp becomes progressively brighter as the blower speed is increased and progressively dimmer as the blower speed is decreased.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary, ignition ON.
    2. Test for less than 1 V between the M8B Blower Motor - Auxiliary control circuit terminal A and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    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.
      • Go to next step: If less than 2 Ω
    4. Replace the K8A Blower Motor Control Module - Auxiliary.
    5. Verify the symptom or DTC was corrected.
      • If the symptom or DTC was not corrected, replace the K33 HVAC Control Module.
      • Go to next step: If the symptom or DTC was corrected
    6. All OK.
    • If the test lamp illuminates, but does not change in brightness 
    1. Ignition OFF, disconnect the X2 harness connector at the K8A Blower Motor Control Module - 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, replace the K8A Blower Motor Control Module - Auxiliary.
    • Go to next step: If the test lamp changes in brightness as the blower speed is changed 
  14. Test or replace the M8B Blower Motor - Auxiliary.
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