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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 >> DTC P0480, P0481, P0691, P0692, P0693, or P0694: Cooling Fan Relay >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect all of the cooling fan Relays. Ignition ON.
    2. NOTE:

    The following tests must be performed on all three fan relay circuits.

  2. Verify that a test lamp illuminates between ground and a relay coil ignition circuit terminal listed below:
    • KR20C Cooling Fan Low Speed Relay terminal 85/2
    • KR20D Cooling Fan High Speed Relay terminal 86/1
    • KR20E Cooling Fan Speed Control Relay terminal 86/1
    • If the test lamp does not illuminate 
    1. Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Remove the test lamp.
    2. Test for less than 2Ω in the ignition circuit of the appropriate cooling fan relay, end to end.
      • If 2Ω or greater, repair the open/high resistance in the 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. Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Remove the test lamp.
    2. Test for infinite resistance between the appropriate cooling fan relay ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance test or replace the appropriate cooling fan relay.
    • If the test lamp illuminates 
    3. NOTE:

    The following tests must be performed on all three fan relay circuits.

  3. Connect a DMM, set on the diode setting, between ground and a relay control circuit terminal listed below:
    • KR20C Cooling fan low speed relay terminal 86/1
    • KR20D Cooling fan high speed relay terminal 85/2
    • KR20E Cooling fan speed control relay terminal 85/2
  4. Verify the DMM reading is greater than 2.5V or displays O.L with the cooling fan Relays commanded OFF with a scan tool.
    • If 2.5V or less  
    1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the appropriate relay coil 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 greater than 2.5V or displays O.L. 
  5. 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 in the appropriate cooling fan relay control circuit end to end.
      • 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  
  6. Test or replace the appropriate cooling fan relay.
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