Electric Cooling Fan Diagnosis

Circuit Description:
Power for the fan motors is supplied through the Cooling Fan fuse in the LH Maxi fuse block. The cooling fan relays are energized when current flows from the Cooling Fan fuse in the IP fuse block through the relay coils to ground through the PCM. The low speed cooling fan relay control circuit is grounded for low speed fan operation. The low speed cooling fan relay and the high speed cooling fan relay control circuits are grounded for high speed operation.

During low speed fan operation the PCM supplies a ground path for the low speed cooling fan relay. This closes the low speed relay contacts, allowing current to flow directly to the R.H. cooling fan and through a resistor to the L.H. cooling fan.
During high speed cooling fan operation the PCM enables both relays, supplying current directly to both cooling fans.

Diagnostic Aids
Check for the following conditions:
^ Poor connection at the PCM, cooling fan relays, or cooling fan motors.
Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness.
Inspect the wiring harness for damage.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Stored diagnostic trouble codes may affect engine cooling fan operation. This diagnostic table may lead to improper diagnosis and replacement of good parts if diagnostic trouble codes are present.
6. Ambient temperature must be greater than 9°C (48°F) before the PCM will enable the cooling fans due to A/C request. The PCM will enable the cooling fans if A/C refrigerant pressure increases regardless of ambient temperature.
44. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.