Operation
The engine coolant fan motor #1 receives power from a 40 amp maxifuse.
The engine coolant fan motor #2 receives power from a 30 amp maxifuse.
Both maxifuses are located in the underhood electrical center.
During low speed operation, the PCM supplies a ground path for the cool
fan 1 relay through the Low Speed Fans control circuit. This energizes the
relay coil, closes the Fan 1 relay contacts, and supplies current to
engine cooling fan #1 motor. The ground path for engine cooling fan #1
is through the series/parallels cooling fan relay, Cool Fan 2 relay,
and engine cooling fan #2 motor. The result is a series circuit with
both fans running at low speed.
To command high speed cooling fan operation, the PCM first supplies
a ground path for the low speed cooling fan, Cool Fan 1, relay through the
Low Speed Fans Control circuit. After a 3 seconds delay, the PCM
supplies a ground path for the series/parallel, Cool Fan 2 relay, and
the high speed cooling fan, Cool Fan #3, relays through the High Speed
Fans Control circuit. During high speed operation, both the engine cooling
fans are supplied current from through their respective maxifuse and each
fan has its own ground.
Important: When certain DTCs are present, the PCM may command the cooling fans
to run all the time. It is important to perform the Powertrain On Board
Diagnostic (OBD) System Check prior to diagnosing the engine cooling
fans.
The PCM will complete the ground path for Cooling Fan relay #1 under
any of the following conditions:
VIN K
| • | When engine coolant temperature exceeds 106°C (223°F). |
| • | When A/C is requested and ambient temperature is more than 50°C (122°F). |
| • | When A/C refrigerant pressure is more than 190 psi (2 volts). |
| • | When the ignition is OFF and engine coolant temperature is more
than 140°C (284°F). |
VIN 1
| • | When engine coolant temperature exceeds 100°C (212°F). |
| • | When A/C is requested and ambient temperature is more than 40°C (104°F). |
| • | When A/C refrigerant pressure is more than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is more
than 140°C (284°F). |
For high speed cooling fans operation, the PCM will delay control of
the Cool Fan 2 relay and Cool Fan #3 relay for 3 seconds. The 3 second
delay ensures that the cooling fan electrical load will not exceed the
capacity of the system. The PCM will complete the ground paths for cooling
fan relays Cool Fan #1, Cool Fan #2 relay, and Cool Fan #3 under any
of the following conditions:
VIN K
| • | When engine coolant temperature exceeds 110°C (230°F). |
| • | When A/C refrigerant pressure is more than 240 psi (2.5 volts). |
VIN K
| • | When engine coolant temperature exceeds 108°C (226°F). |
| • | When A/C refrigerant pressure is more than 240 psi (2.5 volts). |
Diagnosis
If a problem that involves the Low Speed Cooling Fan relay control circuit,
Cooling Fan #1 relay control, exists, DTC P0480 should set. If the
problem affects the High Speed Cooling Fan relay control circuit, Cool
Fan #2 and Cool Fan #3 relay control, DTC P0481 should set. A
problem with the ECT sensor should set DTC P0117, P0118, P1114,
or P1115. Any of these DTCs will affect cooling fan operation and should
be diagnosed before using the Electric Cooling Fan Diagnosis table. The
Electric Cooling Fan Diagnosis table should be used to diagnose the PCM
controlled cooling fans only if no DTC is set.
