Cooling Fan Inoperative (LDK, LHU, LBW, or LAU)
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Cooling Fan Inoperative (LDK, LHU, LBW, or LAU)
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Circuit/System Description
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The engine cooling fan system is composed of two fans, 7 relays, the engine control module (ECM), and the associated wiring. Each fan assembly includes one resistor, which enables the ECM to operate the engine cooling fans at 3 speeds using two control circuits. The ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. Each driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. 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 G106.
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The scan tool cooling fan output control operates as follows:
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Cooling Fan Relay 1 operates both fans at a medium speed
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Cooling Fan Relay 2 and 3 operates both fans at a low speed
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Cooling Fan Relay 1, 2 and 3 operates both fans at a high speed
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When disconnecting 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.
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Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation (LHU/A20NFT, LAU/A28NER)
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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Ignition ON, read the DTC information with a scan tool. DTC P0480 or P0481, P0691, P0692, P0693 or P0694 are not set.
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3.
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Command the cooling fans ON and OFF at low, medium, and high speed with a scan tool. Both cooling fans should turn ON and OFF in each of the commanded states. Refer to Diagnostic Aids.
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1.
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Ignition OFF, disconnect the harness connectors, or remove the following components:
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KR20F Cooling Fan Relay
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KR20E Cooling Fan Speed Control Relay
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KR20L Cooling Fan Speed Control 2 Relay
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G10L Cooling Fan Motor-Left
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G10R Cooling Fan Motor - Right
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2.
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Connect a test lamp between B+ and circuit terminal of the component listed below. The test lamp should illuminate at each terminal.
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G10R Cooling Fan ground circuit terminal 3
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KR20L Relay switched output circuit terminal 8
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3.
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If the test lamp does not illuminate, test the ground circuit for an open circuit/high resistance.
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4.
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Connect a test lamp between B+ and the KR20F relay switched output circuit terminal 30. The test lamp should illuminate.
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5.
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If the test lamp does not illuminate, test the output circuit for an open/high resistance.
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6.
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Ignition ON, connect a test lamp between ground and the KR20 relay terminals listed below. The test lamp should illuminate at each terminal.
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KR20F relay terminal 85
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KR20E relay terminal 86 and 30
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7.
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If the test lamp does not illuminate, test the relay coil ignition circuit for an open/high resistance or for a short to ground.
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8.
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Install the KR20F relay.
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9.
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Connect a test lamp between B+ and the KR20E relay coil control circuit terminal 85.
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10.
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Ignition ON, command the cooling fans ON at medium speed with a scan tool. The test lamp should turn ON.
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11.
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If the test lamp does not illuminate, test for an open/high resistance in the relay coil control circuit. If the circuit tests normal, test or replace the KR20F relay.
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12.
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Ignition OFF, install the KR20E relay.
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13.
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Remove the KR20D Cooling Fan High Speed Relay.
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14.
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Connect a test lamp between ground and the KR20D relay coil ignition circuit terminal 86.
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15.
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Ignition ON, command the cooling fans ON at medium speed with a scan tool. The test lamp should turn ON.
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16.
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If the test lamp does not illuminate, test the KR20D relay coil ignition voltage circuit for an open/high resistance. If the circuit tests normal, test or replace the KR20E relay.
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17.
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Ignition OFF, install the KR20D relay.
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18.
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Ignition ON, Connect a test lamp between ground and the G10 cooling fan harness connector terminal listed below. Command the cooling fans ON at high speed with a scan tool. The test lamp should illuminate at each terminal as commanded.
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G10L Cooling Fan Motor-Left terminal 1
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G10R Cooling Fan Motor-Right terminal 1
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19.
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If the test lamp does not illuminate, test the appropriate relay switched output circuit and B+ supply circuit, for a short to ground or an open/high resistance. If the circuits test normal and the B+ supply fuse is OK, test or replace the KR20C Cooling Fan Low Speed Relay or the KR20D Cooling Fan High Speed Relay, as appropriate.
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20.
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If the circuits test normal and the B+ supply fuse is open, test or replace the appropriate G10 cooling fan motor.
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21.
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Ignition OFF, remove the following relays from the underhood relay block X70:
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KR20M Cooling Fan Left Medium Speed Relay
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KR20N Cooling Fan Right Medium Speed Relay
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22.
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Ignition ON, connect a test lamp between ground and harness terminal 4 of each relay listed below. The test lamp should illuminate at each terminal.
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KR20M Cooling Fan Left Medium Speed Relay
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KR20N Cooling Fan Right Medium Speed Relay
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KR20L Cooling Fan Speed Control 2 Relay
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23.
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If the test lamp does not illuminate, test the relay coil ignition voltage circuit for an open/high resistance, as appropriate.
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24.
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Connect a test lamp between B+ and harness terminal 6 of each relay listed below. Command the cooling fans ON at medium speed. The test lamp should illuminate at each terminal as commanded.
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KR20M Cooling Fan Left Medium Speed Relay
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KR20N Cooling Fan Right Medium Speed Relay
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KR20L Cooling Fan Speed Control 2 Relay
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25.
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It the test lamp does not illuminate, test the relay coil control circuit for an open/high resistance, as appropriate.
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26.
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Ignition OFF, install the following relays:
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KR20M Cooling Fan Left Medium Speed Relay
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KR20N Cooling Fan Right Medium Speed Relay
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27.
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Ignition ON, Connect a test lamp between ground and the G10 cooling fan harness connector terminal listed below. Command the cooling fans ON at medium speed with a scan tool. The test lamp should illuminate at each terminal as commanded.
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G10L Cooling Fan Motor-Left terminal 2
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G10R Cooling Fan Motor-Right terminal 2
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28.
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If the test lamp does not illuminate, test the appropriate relay switched output circuit and B+ supply circuit for an open/high resistance. If the circuits test normal, test or replace the KR20M, or KR20N relay, as appropriate.
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29.
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Ignition OFF, Connect the harness connectors to the G10 cooling fans.
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30.
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Note
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The jumper wire completes the parallel ground circuit for the left cooling fan. Leave the jumper wire in place until instructed.
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Connect a 40 A fused jumper wire between terminal 2 and terminal 8 of the KR20L Speed Control 2 Relay harness connector.
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31.
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Ignition ON, command the cooling fans ON at high speed with a scan tool. Both fans should operate at full speed.
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32.
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If the left fan does not operate, test the series/parallel circuit terminal 2 for an open/high resistance. If the circuit tests normal, test or replace the G10L cooling fan motor.
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33.
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If the right fan does not operate, test or replace the G10R cooling fan motor.
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34.
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Command the cooling fans ON at medium speed with a scan tool. Both fans should operate at a medium speed.
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35.
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If either fan is inoperative, replace the appropriate G10 cooling fan motor.
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36.
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Ignition OFF, remove the jumper wire and install the KR20L Speed Control 2 Relay.
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37.
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Ignition ON, command the cooling fans ON at low speed with a scan tool. Both fans should operate at a reduced speed.
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38.
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If both fans are OFF, test the KR20L series circuit terminal 5 for an open/high resistance.
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39.
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If all of the circuits test normal, test or replace the KR20L Speed Control 2 Relay.
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KR20 Cooling Fan Relay
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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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If not within the specified range, replace the KR20 cooling fan relay.
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4.
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Measure the resistance between the terminals listed below. The DMM should display OL.
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If not the specified range, replace the relay.
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5.
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Install a 20 A fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground. Test for less than 2 Ω between terminals 30 and 87.
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6.
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If greater than the specified range, replace the relay.
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G10 Engine Cooling Fan
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1.
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Ignition OFF, disconnect the harness connector at the G10 engine cooling fan.
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2.
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Connect a jumper wire between ground and the G10 ground circuit terminal 3.
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3.
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Connect a 40 A fused jumper wire between B+ and the G10 fan B+ supply circuit terminal 1. The cooling fan should operate at a High speed.
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4.
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If the cooling fan does not operate, replace the G10 engine cooling fan.
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5.
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Connect a 40 A fused jumper wire between B+ and the G10 fan B+ supply circuit terminal 2. The cooling fan should operate at a reduced speed.
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6.
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If the cooling fan does not operate, replace the G10 engine cooling fan.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
