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Home >> Buick >> 2012 >> Regal GS, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 17 (Engine Cooling System) >> Diagnostic Information and Procedures >> DTC P0480 or P0481 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2011 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the KR20 cooling fan relays listed below:
    • KR20F cooling fan relay
    • KR20A cooling fan medium speed relay
    • KR20D cooling fan high speed relay
    2. NOTE: The following test must be performed on each of the relay coil ignition circuits.
  2. Ignition ON, verify that a test lamp illuminates between ground and the relay coil ignition circuit terminal listed below:
    • KR20F cooling fan relay terminal 85
    • KR20A cooling fan medium speed relay terminal 85
    • If the test lamp does not illuminate, test the relay coil ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
    3. NOTE: The following tests must be performed on all three fan relay control circuits.
  3. Connect the red lead of the DMM to a control circuit terminal listed below. Connect the black lead to ground. Set the DMM on the diode setting. The DMM should display OL.
    • KR20F cooling fan relay terminal 86
    • KR20A cooling fan medium speed relay terminal 86
    • KR20D cooling fan high speed relay terminal 86
    • If less than the specified range, test the appropriate relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
    4. NOTE: The following test must be performed on all three fan relay circuits.
  4. Command the cooling fan relay ON and OFF with a scan tool. The DMM should transition from OL when commanded OFF to less than 1 V when commanded ON.
    • If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance or a short to voltage. If the circuit tests normal, replace the K20 ECM.
  5. If all circuits test normal, test or replace the appropriate KR20 relay.
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