GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2009 🢒 CTS 🢒 Engine 🢒 Engine Cooling 🢒 Cooling Fan Inoperative

Cooling Fan Inoperative with V6

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 consists of one electrical cooling fan, a serviceable resistor module mounted in the cooling fan shroud, and three fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate the fan at low, medium, or high speeds, depending on cooling requirements. The resistor module is a self-contained unit providing a specific resistance through three individual circuits. To activate the fan, the ECM applies ground to the coil side of the applicable fan relays. The cooling fan and fan relays receive battery voltage from the underhood fuse block. The ground path for the operation of the cooling fan is provided at G104.

Diagnostic Aids

When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling System 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, observe the DTC information with a scan tool. Verify that DTC P0480, P0481, P0691, P0692, P0693 or P0694 is not set.
    2. ⇒If any of the listed DTCs are set, Refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694.
  2. Ignition ON, command the fan relays ON and OFF with a scan tool. Verify that the fan operates at low, medium and high speed.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the cooling fan resistor.
  2. Test for less than 5 Ω between the cooling fan motor ground circuit terminal 2 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for and open/high resistance.
  3. Connect a test lamp between the cooling fan motor voltage supply circuit terminal 4 and ground. Command the FC relay 1 ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.
    4. ⇒If the test lamp remains OFF all of the time, test the voltage supply circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the fan relay 1.
    ⇒If the test lamp remains ON all of the time, test the voltage supply circuit for a short to voltage. If the circuit tests normal, test or replace the fan relay 1.
  4. Connect a test lamp between the cooling fan motor voltage supply circuit terminal 3 and ground. Command the FC relay 2 and 3 ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.
    5. ⇒If the test lamp remains OFF all of the time, test the voltage supply circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the fan relay 2.
    ⇒If the test lamp remains ON all of the time, test the voltage supply circuit for a short to voltage. If the circuit tests normal, test or replace the fan relay 2.
  5. Connect a test lamp between the cooling fan motor voltage supply circuit terminal 1 and ground. Command the FC relay 1, 2 and 3 ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.
    6. ⇒If the test lamp remains OFF all of the time, test the voltage supply circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the S/P fan relay.
    ⇒If the test lamp remains ON all of the time, test the voltage supply circuit for a short to voltage. If the circuit tests normal, test or replace the S/P fan relay.
  6. Connect the harness connector at the cooling fan resistor. Disconnect the harness connector at the cooling fan motor.
  7. Connect a test lamp between the voltage supply circuit terminal 1 and the ground circuit terminal 2. Command the cooling fans ON in all 3 speeds. Verify the test lamp illuminates in all 3 speeds.
    8. ⇒If the test does not illuminate in all 3 speeds, replace the cooling fan resistor.
  8. If all circuits/connections test normal, replace the cooling fan motor.

Component Testing
  1. Ignition OFF, disconnect the appropriate cooling fan relay.
  2. Test for 200-240 Ω between terminals 85 and 86 of the relay.
    3. ⇒If not within the specified range, replace the relay.
  3. Test for infinite resistance between the terminals listed below.
    4. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
         ⇒If not the specified value, replace the relay.
  4. Test for less than 2 Ω between terminals 30 and 87A.
    5. ⇒If greater than the specified range, replace the relay.
  5. Install a 20 A fused jumper wire between B+ and relay terminal 85. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
    6. ⇒If greater than the specified range, replace the cooling fan relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Engine Coolant Fan Motor Replacement
    •  Engine Coolant Fan Resistor Replacement