Circuit Description:
The auxiliary cooling fan is controlled by the VCM based on various inputs. Battery voltage is supplied to the auxiliary cooling fan relay. Ignition voltage is supplied to the auxiliary fan relay, coil side. The VCM controls the cooling fan relay by providing a ground path.
Diagnostic Aids
If the driver complaint is 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 gauge indicated overheating. The gauge accuracy can also be checked by the engine coolant temperature (ECT) sensor reading using a scan tool and comparing its reading with the gauge reading.
If the engine is overheating and the cooling fan is ON, the cooling system should be checked. Refer to Engine Overheating in Engine Cooling.
The VCM will command the auxiliary cooling fan ON at 108°C (226°F) and OFF at 102°C (215°F).
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Important: The engine coolant temperature must be below the specified temperature before continuing with this test. Turn ON the ignition leaving the engine OFF. Is the auxiliary fan OFF? | 102°C (215°F) | ||
3 | Command the auxiliary fan motor ON and then OFF with the scan tool. Does the auxiliary fan turn ON and OFF with each command? | -- | Go to Diagnostic Aids | |
4 | Disconnect the auxiliary cooling fan relay. Is the auxiliary fan OFF? | -- | Go to Low Engine Coolant Indicator Inoperative in Engine Cooling | |
5 |
Is the test lamp ON? | -- | Go to Cooling Fan Inoperative - Auxiliary in Engine Cooling | |
Probe the auxiliary fan control circuit at the fan relay connector with a test lamp connected to B+. Is the test lamp ON? | -- | Go to Fan Clutch Diagnosis in Engine Cooling | ||
7 |
Did you find a problem? | -- | ||
8 |
Did you find a problem? | -- | ||
9 |
Did you find a problem? | -- | ||
10 |
Important: The replacement VCM must be programmed. Replace the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
11 |
Does the auxiliary cooling fan turn ON and OFF with each command? | -- | System OK |
