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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 B269A, B269C, or B269D: Heater Coolant Pump Control >> 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 KR31 Coolant Pump Relay-Auxiliary. It may take up to 2 min for all vehicle systems to power down.
  2. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block- Underhood.

    • If the test lamp illuminates 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the ignition circuit terminal 85 and ground.
    • If the test lamp illuminates 
  5. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
  6. Verify the test lamp turns ON and OFF when commanding the G36 Auxiliary Heater Coolant Pump On and Off with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K20 Engine 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
    3. Ignition OFF.
    4. 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 K20 Engine Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K20 Engine 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 K20 Engine Control Module.
    • If the test lamp turns ON and OFF 
  7. Verify a test lamp does not illuminate between the control circuit terminal 87 and ground.
    • If the test lamp illuminates 

      Repair the short to voltage on the circuit.

    • If the test lamp does not illuminate 
  8. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the G36 Auxiliary Heater Coolant Pump. It may take up to 2 min for all vehicle systems to power down.
  9. Test for less than 10 Ω between the ground circuit terminal 1 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 
  10. Connect the harness connector at the G36 Auxiliary Heater Coolant Pump.
  11. Ignition ON, connect a 15 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
  12. Verify the G36 Auxiliary Heater Coolant Pump is activated.
    • If the G36 Auxiliary Heater Coolant Pump does not activate 
    1. Ignition OFF, remove the jumper wire. Disconnect the harness connector at the G36 Auxiliary Heater Coolant Pump.
    2. Test for infinite resistance between the control circuit 2 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, test or replace the G36 Auxiliary Heater Coolant Pump.
    • If the G36 Auxiliary Heater Coolant Pump activates 
  13. Test or replace the KR31 Coolant Pump Relay-Auxiliary.
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