Electric Cooling Fan Diagnosis

Circuit Description:
The electric cooling fan(s) are controlled by the Body Control Module (BCM) which enables the tans through the PCM. The PCM enables the ground path for the three cooling fan relays. The relay(s) are used to control the high current flow to power the cooling fan motors. When minimum cooling is required, the BCM will command the PCM to energize cooling fan relay #1 and since both fans are connected in series through the Mode Control relay, both fans will operate at low speed. When maximum cooling is required, the BCM will command the PCM to energize all three cooling fan relays. Power is supplied to the left fan through the Mode Control relay. The right fan is powered directly through cooling fan relay #2 causing both fans to operate at high speed.

Diagnostic Aids
Check for the following conditions:
^ Poor connection at the PCM, cooling tan 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
Number(s) below refer to the step number(s) on the Diagnostic Table:
2. Stored diagnostic trouble codes may affect engine cooling fans 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 above 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.
77. 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.