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Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis >> Engine Mechanical >> Cooling System (Mechanical) >> Engine Cooling System >> Diagnostic Information and Procedures >> Cooling Fan Inoperative >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect all of the KR20 Cooling Fan Relays.
  2. Ignition ON, verify a test lamp illuminates between ground and the B+ circuit terminals listed below:
    • KR20C Cooling Fan Low Speed Relay B+ circuit terminal 85/2
    • KR20C Cooling Fan Low Speed Relay B+ circuit terminal 30/3
    • KR20D Cooling Fan High Speed Relay B+ circuit terminal 87/5
    • KR20D Cooling Fan High Speed Relay B+ circuit terminal 86/1
    • KR20E Cooling Fan Speed Control Relay B+ circuit terminal 86/1
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Disconnect the appropriate cooling fan fuse or power source.
    2. Test for less than 2Ω between the fuse and the appropriate relay B+ circuit terminal, end to end.
      • If 2Ω or greater, repair the open/high resistance in the B+ circuit.
      • If less than 2Ω, 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. Connect a DMM to the appropriate relay B+ circuit terminal.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the B+ circuit.
      • If infinite resistance
    3. Disconnect the harness connector at the appropriate G10 Cooling Fan Motor.
    4. Test for infinite resistance between the appropriate relay controlled output circuit terminal and ground.
      • KR20C Cooling Fan Low Speed Relay output circuit terminal 87/5
      • KR20D Cooling Fan High Speed Relay output circuit terminal 30/3
      • KR20E Cooling Fan Speed Control Relay circuit terminal 30/3
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the appropriate G10 Cooling Fan Motor.
    • If the test lamp illuminates 
    3. NOTE:

    The following tests must be performed on both fan relay circuits.

  3. Connect a DMM, set on the diode setting, between ground and a relay control circuit terminal listed below:
    • KR20D Cooling Fan High Speed Relay terminal 85/2
    • KR20E Cooling Fan Speed Control Relay terminal 85/2
  4. Verify the DMM reading is less than 1V when commanding the cooling fan Relays ON with a scan tool.
    • If greater than 1V or displays OL. 
    1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module, ignition ON.
    2. Test for less than 1V between the appropriate cooling fan relay control circuit and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V.
    3. Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
    4. Test for less than 2Ω between the KR20E Cooling Fan Speed Control Relay terminal 85/2 and KR20D Cooling Fan High Speed Relay terminal 85/2.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K20 Engine Control Module.
    • If less than 1V  
  5. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the G10L Cooling Fan Motor-Left. It may take up to 2 minutes for all vehicle systems to power down.
  6. Test for less than 5Ω between the circuits listed below and ground:
    • G10L Cooling Fan Motor-Left terminal A
    • KR20E Cooling Fan Speed Control Relay terminal 87/5
    • If 5Ω or greater 
    1. Ignition OFF and all vehicle systems OFF, it may take up to 2minutes for all vehicle systems to power down.
    2. Test for less than 2Ω in the appropriate ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 5Ω 
  7. Connect the harness connector at the G10L Cooling Fan Motor-Left.
  8. Connect a 50A fused jumper between the KR20D Cooling Fan High Speed Relay terminals 30/3 and 87/5.
  9. Ignition ON, verify the G10L Cooling Fan Motor-Left is activated at high speed.
    • If the cooling fan does not activate or jumper fuse opens 
    1. Disconnect the harness connector at the G10L Cooling Fan Motor-Left.
    2. Test for less than 2Ω in the circuit between KR20D Cooling Fan High Speed Relay terminal 30/3 and the G10L Cooling Fan Motor-Left terminal B.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the G10L Cooling Fan Motor-Left.
    • If the cooling fan activates 
  10. Ignition OFF, connect a fused jumper between the KR20E Cooling Fan Speed Control Relay switch circuit terminal 30/3 and the ground circuit terminal 87/5.
  11. Connect a 40A fused jumper between the KR20C Cooling Fan Low Speed Relay terminals 30/3 and 87/5.
  12. Ignition ON, verify the G10R Cooling Fan Motor-Right is activated at high speed.
    • If the cooling fan does not activate 
    1. Disconnect the harness connector at the G10R Cooling Fan Motor-Right.
    2. Test for less than 2Ω in the circuit between KR20C Cooling Fan Low Speed Relay terminal 87/5 and the G10R Cooling Fan Motor-Right terminal B.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω
    3. Test for less than 2Ω in the circuit between KR20E Cooling Fan Speed Control Relay terminal 30/3 and the G10R Cooling Fan Motor-Right terminal A.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the G10R Cooling Fan Motor-Right.
    • If the cooling fan activates 
  13. Ignition OFF, Install the KR20E Cooling Fan Speed Control Relay.
  14. Ignition ON, verify both fan motors activate at low speed.
    • If both cooling fans do not activate at low speed 
    1. Disconnect both cooling fan motor harness connectors and the KR20E Cooling Fan Speed Control Relay.
    2. Test for less than 2Ω in circuit between KR20E Cooling Fan Speed Control Relay terminal 87A/4 and the G10L Cooling Fan Motor-Left terminal B.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω
    3. Test for infinite resistance between KR20E Cooling Fan Speed Control Relay terminal listed below and ground.
      • KR20E Cooling Fan Speed Control Relay terminal 30/3
      • KR20E Cooling Fan Speed Control Relay terminal 87A/4
      • If less than infinite, repair the short to ground in the circuit.
      • If infinite, replace the KR20E Cooling fan speed control relay.
    • If both cooling fans activate 
  15. Ignition OFF, test or replace the cooling fan relay listed below as appropriate:
    • KR20C Cooling Fan Low Speed Relay
    • KR20D Cooling Fan High Speed Relay
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