Circuit/System Testing

WARNING: This page is about a different car, the 2007 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: Circuit/System Verification must be performed first or misdiagnosis may result.

Ignition OFF, disconnect the connector from the cooling fan speed control module.
Ignition OFF, install a test lamp between the cooling fan speed control circuit terminal 6 and B+. The lamp should be OFF.
- If the lamp is ON, test the cooling fan speed control circuit for a short to ground. If the circuit tests normal, replace the ECM.
Ignition ON, command the cooling fan speed from 0-100 percent with a scan tool. The brightness of the lamp should change with the commanded states.
- If the lamp brightness does not change correctly, test the cooling fan speed control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
Ignition OFF, measure between the cooling fan speed control module ground circuit terminal 2 at the harness connector and ground for less than 1 ohm of resistance.
- If greater than the specified range repair the module ground circuit for open/high resistance.
Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
Install appropriately fused jumpers between the cooling fan harness connector terminals 1 and 4 power and ground. The cooling fan should activate at full speed.
- If the cooling fan does not activate, replace the cooling fan.
If the ECM, fan, and all circuits test normal, replace the cooling fan speed control module.