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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1864 (Engine Cooling System) >> Diagnostic Information and Procedures >> DTC P0480 or P0481 (2.2L and 2.4L) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the affected relay.
  2. Ignition ON, connect a test lamp between the positive terminal at the battery and the relay control circuit terminal.
  3. Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Connect a 30A fused jumper wire between the positive voltage terminal at the battery and the fan voltage supply circuit terminal and verify fan activation.
    • If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fan.
  5. Ignition ON, connect a 30A fused jumper wire between the relay switch voltage supply circuit terminal and the fan voltage supply circuit terminal and verify fan activation.
    • If the fan does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and it's fuse is open, replace the relay.
  6. Ignition ON, verify that a test lamp illuminates between the relay coil voltage supply circuit terminal and ground.
    • If the test lamp does not illuminate, test the relay coil voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the relay.
  7. If all circuits and the ECM test normal, replace the affected relay.
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