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Home >> Isuzu >> 2007 >> Ascender RWD >> Repair and Diagnosis >> Engine Mechanical >> Cooling System (Mechanical) >> Engine Cooling System >> Diagnostic Information and Procedures >> DTC P0480 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the fan relay.
  2. Measure between the fan relay ground circuit terminal and ground for less than 3 ohms.
    • If more than the specified range, test the ground circuit for an open/high resistance.
  3. Operate the engine at 2,000 RPM for 2 minutes. The fan should be quiet to indicated the clutch is disengaged.
    • If not disengaged, test the cooling fan clutch supply voltage circuit for a short to voltage. If the circuit tests normal, replace the clutch.
  4. Ignition OFF, install a 10A fused jumper wire between the positive terminal at the battery and the cooling fan clutch supply voltage circuit terminal.
  5. Operate the engine at 2,000 RPM for 2 minutes. The fan should be loud to indicated the clutch is engaged.
    • If not engaged, test the cooling fan clutch supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the clutch.
  6. Ignition OFF, install a 10A fused jumper wire between the relay voltage supply circuit terminal and the cooling fan clutch supply voltage circuit terminal.
  7. Operate the engine at 2,000 RPM for 2 minutes. The fan should be loud to indicated the clutch is engaged.
    • If not engaged, test the relay voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.
  8. Connect a test lamp between the positive terminal at the battery and the cooling fan clutch relay control circuit terminal.
  9. Engine RUNNING at 2,000 RPM, command the cooling fan clutch from 10 to 80 percent. The test lamp should flash at approximately 2 Hz as its brightness varies from dim to bright.
    • If the lamp does not flash or vary correctly, test the cooling fan clutch control circuit for a short to ground, a short to voltage or an open/high resistance. If the circuit tests normal, replace the control module.
  10. If all circuits and the control module test normal, replace the relay.
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