Cooling Fan Inoperative (LLU)
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Cooling Fan Inoperative (LLU)
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Circuit/System Description
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The engine cooling fan system is composed of one fan, 5 relays, the engine control module (ECM), and the associated wiring. The fan assembly includes two resistors, which enable the fan to operate at 3 speeds.
In low speed operation, the ECM provides ground from ECM terminal X2 44 (LDE/2H0), or terminal X2 14 (LLU). The cooling fan relay activates and provides ground to the coils of the cooling fan medium speed 2 relay and the cooling fan speed control relay. The cooling fan speed control relay activates and provides power to the coil of the cooling fan high speed relay. The cooling fan high speed relay remains inactive because ECM terminal X2 15 (LDE/2H0) or terminal X2 12 (LLU) is not grounded. The cooling fan medium speed 2 relay provides power to the cooling fan motor through cooling fan terminal 2 and the internal fan resistor.
In medium speed operation, the ECM provides ground to ECM terminal X2 15 (LDE/2H0) or terminal X2 12 (LLU). The cooling fan high speed relay remains inactive because power is not provided to the coil from the cooling fan speed control relay. The cooling fan medium speed 1 relay activates and provides power to the cooling fan motor through cooling fan terminal 3 and the internal fan resistor.
In high speed operation, the ECM provides ground to ECM terminals X2 15 and X2 44 (LDE/2H0) or terminals X2 12 and X2 14 (LLU). As previously described, power is now provided to both cooling fan terminals 2 and 3. In addition, power and ground are now provided to the coil of the cooling fan high speed relay. The Cooling Fan High Speed Relay activates and provides power to the cooling fan motor through cooling fan terminal 4.
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
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Circuit/System Verification
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1.
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Verify that DTCs P0480 00, or P0481 00 are not set.
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2.
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If a DTC is set, refer to
DTC P0480, P0481, P0691, P0692, P0693, or P0694 (LLU)
DTC P0480, P0481, P0691, P0692, P0693, or P0694 (LBW, LAU)
for further diagnosis.
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3.
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Command the Fan Relay 1 ON and OFF with a scan tool. The fan should turn ON at low speed and OFF with each command.
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4.
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If the fan does not operate correctly, go to low speed operation malfunction.
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5.
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Command the Fan Relay 2 and 3 ON and OFF with a scan tool. The fan should turn ON at medium speed and OFF with each command.
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6.
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If the fan does not operate correctly, go to medium speed operation malfunction.
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7.
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Command the Fan Relay 1, 2, and 3 ON and OFF with a scan tool. The fan should turn ON at high speed and OFF with each command.
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8.
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If the fan does not operate correctly, go to high speed operation malfunction.
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Note
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You must perform the circuit/system verification before proceeding with circuit/system testing.
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Low Speed Malfunction
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1.
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Ignition OFF, disconnect the relays listed below:
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KR20B Cooling Fan Medium Speed 2 Relay
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KR20E Cooling Fan Speed Control Relay
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KR20F Cooling Fan Relay
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2.
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Test for less than 1 Ω between the relay controlled output circuit terminal of the KR20F Cooling Fan Relay and ground.
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3.
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If greater than the specified range, test the output circuit for an open/high resistance.
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4.
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Verify that a test lamp illuminates between the relay coil ignition circuit terminal of the KR20B Cooling Fan Medium Speed 2 Relay connector and ground.
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5.
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If the test lamp does not illuminate, test the relay coil ignition circuit for an open/high resistance.
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6.
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Verify that a test lamp illuminates between the relay switch B+ circuit terminal of the KR20B Cooling Fan Medium Speed 2 Relay connector and ground.
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7.
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If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled output circuit terminals of the relay connectors listed below for a short to ground
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KR20A Cooling Fan Medium Speed 1 Relay
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KR20B Cooling Fan Medium Speed 2 Relay
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8.
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Install a 10 A fused jumper wire between the relay coil ignition circuit terminal and the relay coil control circuit terminal of the KR20B Cooling Fan Medium Speed 2 Relay connector.
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9.
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Verify that a test lamp illuminates between the relay switch ignition circuit terminal and the relay controlled output circuit terminal at the KR20E Cooling Fan Speed Control Relay connector.
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10.
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If the test lamp does not illuminate, test the relay switch ignition circuit terminal at the KR20F Cooling Fan Relay connector for a short to ground or an open/high resistance.
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11.
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Disconnect the harness connector at the G10 Cooling Fan Motor.
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12.
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Test for less than 1.0 Ω between the G10 Cooling Fan Motor ground circuit terminal 1 and ground.
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13.
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If greater than the specified range, test the ground circuit for an open/high resistance.
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14.
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Connect the harness connector at the G10 Cooling Fan Motor.
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15.
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Connect a 60 A fused jumper wire between the relay switch B+ circuit terminal and the relay controlled output circuit terminal of the KR20B Cooling Fan Medium Speed 2 Relay connector. Verify the cooling fan is activated at low speed.
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16.
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If the cooling fan does not activate at low speed, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the cooling fan.
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17.
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If all circuits test normal, test the relays listed below for correct operation and replace the faulty relay:
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KR20F Cooling Fan Relay
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KR20B Cooling Fan Medium Speed 2 Relay
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Medium Speed Malfunction
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1.
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Ignition OFF, disconnect the KR20A Cooling Fan Medium Speed 1 Relay.
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2.
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Verify that a test lamp illuminates between the relay coil ignition circuit terminal and ground.
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3.
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If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
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4.
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Verify that a test lamp illuminates between the relay switch B+ circuit terminal and ground.
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5.
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If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
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6.
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Connect a 60 A fused jumper wire between the relay switch B+ circuit terminal and the relay controlled output circuit terminal. Verify the cooling fan is activated at medium speed.
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7.
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If the cooling fan does not activate at low speed, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the G10 Cooling Fan Motor.
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8.
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Test for less than 1 V between the relay coil control circuit terminal and ground.
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9.
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If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, test the KR20E Cooling Fan Speed Control Relay for correct operation. If the relay tests normal, replace the K20 Engine Control Module.
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10.
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If all circuits test normal, test or replace the KR20A Cooling Fan Medium Speed 1 Relay.
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11.
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If greater than the specified range, test the ground circuit for an open/high resistance.
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High Speed Malfunction
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1.
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Ignition OFF, disconnect the relays listed below:
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KR20D Cooling Fan High Speed Relay
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KR20E Cooling Fan Speed Control Relay
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2.
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Verify that a test lamp illuminates between the relay coil ignition circuit terminal of the KR20E Cooling Fan Speed Control Relay connector and ground.
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3.
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If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
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4.
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Verify that a test lamp illuminates between the relay switch ignition circuit terminal of the KR20E Cooling Fan Speed Control Relay connector and ground.
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5.
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If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
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6.
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Install a 10 A fused jumper wire between the relay switch ignition circuit terminal and the relay controlled output circuit terminal of the KR20E Cooling Fan Speed Control Relay connector.
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7.
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Verify that a test lamp illuminates between the relay coil ignition circuit terminal of the KR20D Cooling Fan High Speed Relay connector and ground.
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8.
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If the test lamp does not illuminate, test the ignition circuit terminal for an open/high resistance.
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9.
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Verify that a test lamp illuminates between the relay switch B+ circuit terminal of the KR20D Cooling Fan High Speed Relay connector and ground.
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10.
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If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the G10 Cooling Fan Motor.
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11.
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Connect a 60 A fused jumper wire between the relay switch B+ circuit terminal and the relay controlled output circuit terminal to the KR20D Cooling Fan High Speed Relay connector. Verify the cooling fan is activated at high speed.
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12.
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If the cooling fan does not activate at low speed, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the G10 Cooling Fan Motor.
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13.
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If all circuits test normal, test the relays listed below for correct operation and replace the faulty relay:
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KR20E Cooling Fan Speed Control Relay
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KR20D Cooling Fan High Speed Relay
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Relay Test
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1.
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Ignition OFF, disconnect the cooling fan relay.
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2.
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Test for 70-110 Ω between terminals 85 and 86.
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3.
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Test for infinite resistance between the following terminals:
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If not the specified range, replace the relay.
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4.
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Test for less than 2 Ω between terminals 30 and 87A.
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5.
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If greater than the specified range, replace the relay.
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6.
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Install a 20 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
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7.
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If greater than the specified range, replace the relay.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
