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Circuit/System Testing

WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.

Inoperative in All Speeds

  1. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.
  2. Verify a test lamp illuminates between the ground circuit terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Ignition OFF, remove the test lamp.
    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.
    • Go to next step: If the test lamp illuminates 
  3. Test or replace the G10 Cooling Fan Motor.

Low/High Speed Inoperative

  1. Ignition OFF, disconnect the cooling fan relays listed below, ignition ON.
    • KR20C Cooling Fan Low Speed Relay
    • KR20D Cooling Fan High Speed Relay
  2. Verify a test lamp illuminates between the KR20C Cooling Fan Low Speed Relay B+ circuit terminal 30 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 B+ 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 B+ circuit.
      • Go to next step: If infinite resistance
    3. Disconnect the harness connector at the G10 Cooling Fan Motor.
    4. Test for infinite resistance between the relay circuit terminals listed below and ground.
      • KR20D Cooling Fan High Speed Relay B+ circuit terminal 30
      • KR20D Cooling Fan High Speed Relay output circuit terminal 87
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance, test or replace the G10 Cooling Fan Motor.
    • Go to next step: If the test lamp illuminates 
  3. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.
  4. Remove the test lamp and reconnect the KR20C Cooling Fan Low Speed Relay, ignition ON.
  5. Command the cooling fan ON at low speed.
  6. Verify a test lamp illuminates between the KR20D Cooling Fan High Speed Relay B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, remove the test lamp and the KR20C Cooling Fan Low Speed Relay.
    2. Test for less than 2 Ω between the KR20C Cooling Fan Low Speed Relay terminal 87 and KR20D Cooling Fan High Speed Relay terminal 30.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the KR20C Cooling Fan Low Speed Relay.
    • Go to next step: If the test lamp illuminates 
  7. Ignition OFF, remove the test lamp and reconnect the KR20D Cooling Fan High Speed Relay.
  8. Command the cooling fan ON at high speed with a scan tool.
  9. Verify a test lamp illuminates between the G10 Cooling Fan Motor terminals listed below and ground.
    • G10 Cooling Fan Motor low speed circuit terminal 2
    • G10 Cooling Fan Motor high speed circuit terminal 4
    • If the test lamp does not illuminate at terminal 4 
    1. Ignition OFF, remove the test lamp and disconnect the KR20D Cooling Fan High Speed Relay.
    2. Test for less than 2 Ω in the KR20D Cooling Fan High Speed Relay output circuit terminal 87, 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 KR20D Cooling Fan High Speed Relay.
    • If the test lamp does not illuminate at terminal 2 
    1. Ignition OFF, remove the test lamp and disconnect the KR20C Cooling Fan Low Speed Relay.
    2. Test for less than 2 Ω in the KR20C Cooling Fan Low Speed Relay output circuit terminal 87, end to end.
      • If 2 Ω or greater and the 30 A fuse is good, repair the open/high resistance in the output circuit.
      • If 2 Ω or greater and the 30 A fuse is open, test the output circuit for a short to ground. If the circuit tests normal, test or replace the G10 Cooling Fan Motor.
    • Go to next step: If the test lamp illuminates at both terminals 
  10. Test or replace the G10 Cooling Fan Motor.

Medium Speed Inoperative

  1. Ignition OFF, disconnect the KR20P Cooling Fan Medium Speed Relay, ignition ON.
  2. Verify a test lamp illuminates between the KR20P Cooling Fan Medium Speed Relay B+ circuit terminal 30 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 terminal 30, 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 in the circuit.
      • Go to next step: If infinite resistance.
    3. Disconnect the harness connector at the G10 Cooling Fan Motor.
    4. Test for infinite resistance between the KR20P Cooling Fan Medium Speed Relay output circuit terminal 87 and ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance, test or replace the G10 Cooling Fan Motor.
    • Go to next step: If the test lamp illuminates 
  3. Ignition OFF, remove the test lamp and reconnect the KR20P Cooling Fan Medium Speed Relay.
  4. Disconnect the harness connector at the G10 Cooling Fan Motor, ignition ON.
  5. Command the cooling fan ON at medium speed with a scan tool.
  6. Verify a test lamp illuminates between the G10 Cooling Fan Motor medium speed circuit terminal 3 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, remove the test lamp and disconnect the KR20P Cooling Fan Medium Speed Relay, ignition ON.
    2. Test for less than 2 Ω in the KR20P Cooling Fan Medium Speed Relay output circuit terminal 87, 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 KR20P Cooling Fan Medium Speed Relay.
      • Go to next step: If the test lamp illuminates 
  7. Test or replace the G10 Cooling Fan Motor.
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