Buick Regal Owners & Service Manuals

Buick Regal: Cooling Fan Inoperative (LGX)

Diagnostic Instructions

  • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
  • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
  • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The engine cooling fan system is composed of two electric cooling fans and a cooling fan control module.

The engine control module (ECM) controls the fan speeds by sending a pulse width modulated (PWM) signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the cooling fan motors in relation to the pulse width modulated signal, which enables cooling fan operations at variable speeds. The ECM will only operate the cooling fans at certain percentages to prevent undesirable noise and vibration. The cooling fan control module is thermally protected to prevent module damage in the case of a short circuit condition in the cooling fan motors.

Diagnostic Aids

  • The cooling fans will not operate when the scan tool Cooling Fan Motor Command parameter displays less than 4 %. This is a normal condition.
  • A delay or ramp up of approximately 12 seconds may occur before the cooling fans activate or change speeds when being commanded with a scan tool.
  • The cooling fan Control Function operates as described below when the ignition is ON, and engine is OFF:
    • Command State 1 operates the cooling fans at approximately 18 %
    • Command State 2 operates the cooling fans at approximately 54 %
    • Command State 3 operates the cooling fans at approximately 67 %
    • Command State 4 operates the cooling fans at approximately 85 %
    • Command State 5 operates the cooling fans at approximately 90 %
  • During normal operating conditions the ECM may initially activate the cooling fans at 4 or 5 % and then increase to the percentages indicated above, as needed, to satisfy powertrain cooling requirements. Generally, the ECM will operate the cooling fans at the specified percentages but, may scale the percentages either higher or lower in response to generator demand.
  • When operating the cooling fans with a scan tool, the Commanded States 1 - 5 should be exercised in order, from OFF to High or High to OFF. The cooling fan control module may disable the cooling fans if a Commanded State is skipped.

Reference Information

Schematic Reference

Engine Heating/Cooling Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

  • Circuit Testing
  • Connector Repairs
  • Testing for Intermittent Conditions and Poor Connections
  • Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.

2. Verify that DTC P0480, P0691, or P0692, is not set.

  • If a DTC is set

Refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 (LTG) or DTC P0480, P0481, P0691, P0692, P0693, or P0694 (LGX).

  • Go to next step: If no DTC is set.

NOTE: A slight delay may occur before the cooling fan activates.

3. Verify the G10 Cooling Fan Motors activate and increases in speed with each command using a scan tool.

  • The cooling fans do not activate or increase in speed

Refer to Circuit/System Testing

  • Go to next step: The cooling fans activate and increases in speed

4. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector G10L Cooling Fan Motor or G10R Cooling Fan Motor.

2. Verify that a test lamp illuminates between the ground circuit terminal 2 and B+ of the inoperative G10 Cooling Fan Motor.

  • If the test lamp does not illuminate
  1. Ignition OFF, and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 2 Ω in the ground circuit end to end.
    • If 2 Ω or greater, repair the open/high resistance in the circuit.
    • If less than 2 Ω, repair the open/high resistance in the ground connection.
  • Go to next step: If the test lamp illuminates

3. Test or replace the inoperative G10 Cooling Fan Motor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  • Engine Coolant Fan Replacement (2.0L LTG) or Engine Coolant Fan Replacement (3.6L LGX) for G10 Cooling Fan Motor replacement.
  • Control Module References

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