Electric Cooling Fan Diagnosis

Diagnostic Chart:

CIRCUIT DESCRIPTION:

The cooling fans are controlled by the PCM based on various inputs. Battery voltage is supplied to the primary and secondary cooling fan relays (switch side). Ignition voltage is supplied to the primary and secondary cooling fan relays (coil side). The PCM controls the cooling fan relays by providing a ground path. The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set. For the Fan schematic, refer to Fan Controls-w/o VO8 or Fan Controls-With V08. Electrical Diagrams

DIAGNOSTIC AIDS

If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the warning indicator light, or engine coolant temperature gage indicated overheating. The gage accuracy can also be checked by comparing the Engine Coolant Temperature (ECT) sensor reading using a scan tool and comparing its reading with the gage reading. If the engine is actually overheating and the gage indicated overheating, but the cooling fan is not coming ON, the Engine Coolant Temperature (ECT) sensor has probably shifted out of calibration and should be replaced. If the engine is overheating and the cooling fans are ON, the cooling system should be checked. The PCM will command fan 1 ON at 107°C (225°F) and OFF at 103°C (218°F) and, fan 2 ON at 111°C (232°F) and OFF at 107°C (225°F).

TEST DESCRIPTION

Number(s) below refer to number(s) on the diagnostic table.

2. The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set. Go to applicable DTC Table first before proceeding with this table.

3. Allow engine coolant temperature to cool below 100°C (212°F) before proceeding with diagnosis diagnoses.