Operation
the Engine Coolant Fan Motor #1 receives power from a 40 amp maxifuse.
The Engine Coolnat 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 Coolant Fan #1 Relay control circuit. This energizes
the relay coil, closes the Fan 1 relay contacts, and supplies current to the
primary cooling fan. The ground path for the primary cooling fan is through
the series/paralles cooling fan relay (Cool Relay) and secondary cooling fan
motor. The result is a seris 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
Coolant Fan #1 Relay Control circuit. After a 3 seconds delay, the PCM supplies
a ground path for the series/parallel (Cool Relay) and the high speed cooling
fan (Cool Fan #2) relays through the Coolant Fan #2 Relay Control circuit.
During high speed operation, both the primary and the secondary cooling fans
are supplied current from through their respective maxifuse and each fan has
its own ground.
Important: When certain Diagnostic Trouble Codes (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 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 greater than
11°C (52°F). |
| • | When A/C refrigerant pressure is greater than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is greater
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 greater than
11°C (52°F). |
| • | When A/C refrigerant pressure is greater than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is greater
than 140°C (284°F). |
For high speed cooling fans operation, the PCM will delay control of
the Cool Relay and Cool Fan #2 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 Relay, and Cool Fan #2 under any of the following conditions:
VIN K
| • | When engine coolant temperature exceeds 110°C (230°F). |
| • | When A/C refrigerant pressure is greater than 240 psi (2.5 volts). |
VIN 1
| • | When engine coolant temperature exceeds 108°C (226°F). |
| • | When A/C refrigerant pressure is greater than 240 psi (2.5 volts). |
Diagnosis
If a problem that involves the low speed cooling fan relay control circuit
(cooling fan relay #1 control) exists, DTC P1651 should set. If the problem
affects the high speed cooling fan relay control circuit (Cool Relay and Cool
Fan #2 Relay control), DTC P1652 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.
