Malibu V6-191 3.1L VIN M SFI (1997)
Accessory Signal: Description and Operation
Cooling Fan Control Signal
DESCRIPTION
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant
(R134a) flowing through the A/C condenser.
OPERATION
The Powertrain Control Module (PCM) controls the operation of the cooling fans. This is accomplished by providing a ground path for the cooling fan
relay coils within the PCM. The relay contacts will close and complete the circuit between the fusible link at the battery junction block and the fan
motors. Whenever there is a fan ON request both fans will be running.
Power is supplied to the cooling fan motors through a fusible link and three 60 AMP maxifuses. The 60 AMP maxifuses are located in the underhood
electrical center. The PCM Output Driver Module B output 1 is used to control Fan 1 operation. The PCM Output Driver Module B output 2 is used to
control Fan 2 operation. The Driver Module outputs are monitored by the PCM. If Diagnostic Trouble Codes P1651 or P1652 are present follow the
appropriate diagnostic tables prior to performing Electric Cooling Fans Diagnosis / System Diagnostic Tables. See: Testing and Inspection
The PCM will complete the ground path for the low speed cooling fans (Fan 1) relay 1 under the following conditions:
^
When engine temperature exceeds 105°C (221°F).
^
When A/C is requested (ambient temperature must be above 9°C (48°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).
The PCM will complete the ground paths for the high speed cooling fans (Fan 2) relays 1, 2 and 3 under the following conditions:
^
When engine temperature exceeds 113°C (235°F).
^
When A/C refrigerant pressure is greater than 275 psi (2.9 volts).
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. See: Testing and Inspection
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 (cooling fan relay #2 and #3 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. See: Testing and Inspection
