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Radiator Fan System: Inspection

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Operating condition: 

Radiator fan operates depending on the radiator fan speed related to engine coolant temperature or the radiator fan speed related to A/C compressor load, whichever is higher as a load condition.

Fig 1: Radiator Fan Speed / Engine Coolant Temperature Graph
G11586240Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Radiator Fan Speed To A/C Compressor Load Graph
G11586241Courtesy of SUBARU OF AMERICA, INC.

Diagnosis: 

Radiator main fan and radiator sub fan do not rotate under the above operating conditions.

Step Check Yes No
1 CHECK OPERATION OF RADIATOR FAN.
  1. Turn the ignition switch to OFF.
  2. Connect the delivery mode fuse.
 Does the radiator main fan rotate? Go to step 2  . Go to step 3  .
2 CHECK OPERATION OF RADIATOR FAN. 
  1. Turn the ignition switch to OFF.
  2. Connect the delivery mode fuse.
 Does the radiator sub fan rotate? Radiator main fan system is normal. Go to step 11 
3 CHECK MAIN FAN RELAY. 
  1. Turn the ignition switch to OFF.
  2. Remove the main fan relay from the relay holder.
  3. Measure the resistance between terminals on the main fan relay switch side.
 Is the resistance 1 MΩ or more? Go to step 4  Replace the main fan relay. Ref. to RELAY AND FUSE
4 CHECK MAIN FAN RELAY. 
  1. Connect the main fan relay coil side terminal to the battery.
  2. Measure the resistance between terminals on the main fan relay switch side.
 Is the resistance less than 1 Ω? Go to step 5  Replace the main fan relay. Ref. to RELAY AND FUSE
5 CHECK POWER SUPPLY FOR ECM. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM.
  3. Set the ST between the engine control module (ECM) and engine harness. Ref. to CAUTION , General Description.
  4. Turn the ignition switch to ON.
  5. Measure the voltage between ECM terminal and chassis ground.

Connector & terminal 
(B134) No. 39 (+) - Chassis ground (-): 		 Is the voltage 10 V or more? Go to step 6  Repair the power supply line.
6 CHECK POWER SUPPLY FOR RADIATOR FAN CONTROL MODULE (MAIN). 
  1. Turn the ignition switch to OFF.
  2. Remove the ST, and connect the connector to ECM.
  3. Disconnect the connector from radiator fan control module (main).
  4. Turn the ignition switch to ON.
  5. Measure the voltage between radiator fan control module (main) terminal and chassis ground.

Connector & terminal 
(F106) No. 1 (+) - Chassis ground (-): 		 Is the voltage 10 V or more? Go to step 7  Repair the power supply line.
7 CHECK HARNESS BETWEEN ECM AND RADIATOR FAN CONTROL MODULE (MAIN). 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM.
  3. Measure the resistance between radiator fan control module (main) and ECM connector.

Connector & terminal 
(B134) No. 41 - (F106) No. 2: 		 Is the resistance less than 1 Ω? Go to step 8  Repair the open circuit of harness between ECM and radiator fan control module (main).
8 CHECK GROUND CIRCUIT FOR RADIATOR FAN CONTROL MODULE (MAIN). 
  1. Connect the connector to ECM and radiator fan control module (main).
  2. Measure the resistance between radiator fan control module (main) connector and chassis ground.

Connector & terminal 
(F106) No. 3 - Chassis ground: 		 Is the resistance less than 5 Ω? Go to step 9  Repair the open circuit of harness between radiator fan control module (main) connector and chassis ground.
9 CHECK MAIN FAN MOTOR. 
  1. Disconnect the connector from radiator fan control module (main).
  2. Connect the battery positive (+) terminal to terminal No. 1 of the main fan motor, and the ground (-) terminal to terminal No. 2.
 Does the main fan motor rotate? Go to step 10  Replace the main fan motor. Ref. to RADIATOR FAN AND FAN MOTOR ASSEMBLY 
10 CHECK OUTPUT SIGNAL FROM ECM. 
  1. Turn the ignition switch to OFF.
  2. Connect the delivery mode fuse.
  3. Turn the ignition switch to ON.
  4. Check the output waveform using oscilloscope. Ref. to RADIATOR FAN CONTROL OUTPUT WAVEFORM , Radiator Fan System.

Connector & terminal 
(B134) No. 41 (+) - Chassis ground (-): 		 Is waveform being output? Replace the radiator fan control module (main). Ref. to RADIATOR FAN CONTROL MODULE (MAIN) , REMOVAL, Radiator Fan Control Unit. Replace the ECM. Ref. to ENGINE CONTROL MODULE (ECM)
NOTE: After replacing the ECM, check again from step  1
11 CHECK SUB FAN RELAY. 
  1. Turn the ignition switch to OFF.
  2. Remove the sub fan relay from the relay holder.
  3. Measure the resistance between terminals on the sub fan relay switch side.
 Is the resistance 1 MΩ or more? Go to step 12  Replace the sub fan relay. Ref. to RELAY AND FUSE
12 CHECK SUB FAN RELAY. 
  1. Connect the battery to the terminal on the sub fan relay coil side.
  2. Measure the resistance between terminals on the sub fan relay switch side.
 Is the resistance less than 1 Ω? Go to step 13  Replace the sub fan relay. Ref. to RELAY AND FUSE
13 CHECK POWER SUPPLY FOR RADIATOR FAN CONTROL MODULE (SUB). 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from radiator fan control module (sub).
  3. Turn the ignition switch to ON.
  4. Measure the voltage between radiator fan control module (sub) terminal and chassis ground.

Connector & terminal 
(F22) No. 1 (+) - Chassis ground (-): 		 Is the voltage 10 V or more? Go to step 14  . Repair the power supply line.
14 CHECK HARNESS BETWEEN ECM AND RADIATOR FAN CONTROL MODULE (SUB). 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM.
  3. Measure the resistance between radiator fan control module (sub) and ECM connector.

Connector & terminal 
(B134) No. 40 - (F22) No. 2: 		 Is the resistance less than 1 Ω? Go to step 15  . Repair the open circuit of harness between ECM and radiator fan control module (sub).
15 CHECK GROUND CIRCUIT FOR RADIATOR FAN CONTROL MODULE (SUB). 
  1. Connect the connector to ECM and radiator fan control module (sub).
  2. Measure the resistance between radiator fan control module (sub) connector and chassis ground.

Connector & terminal 
(F22) No. 3 - Chassis ground: 		 Is the resistance less than 5 Ω? Go to step 16  Repair the open circuit of harness between radiator fan control module (sub) connector and chassis ground.
16 CHECK SUB FAN MOTOR. 
  1. Disconnect the connector from radiator fan control module (sub).
  2. Connect the battery positive (+) terminal to terminal No. 1 of the sub fan motor, and the ground (-) terminal to terminal No. 2.
 Does the sub fan motor rotate? Go to step 17  Replace the sub
fan motor. Ref. to RADIATOR FAN AND FAN MOTOR ASSEMBLY 
17 CHECK OUTPUT SIGNAL FROM ECM. 
  1. Turn the ignition switch to OFF.
  2. Connect the delivery mode fuse.
  3. Turn the ignition switch to ON.
  4. Check the output waveform using oscilloscope. Ref. to RADIATOR FAN CONTROL OUTPUT WAVEFORM , Radiator Fan System.

Connector & terminal 
(B134) No. 40 (+) - Chassis ground (-): 		 Is waveform being output? Replace the radiator fan control module (sub). Ref. to RADIATOR FAN CONTROL MODULE (SUB) , REMOVAL, Radiator Fan Control Unit. Replace the ECM. Ref. to ENGINE CONTROL MODULE (ECM)
NOTE: After replacing the ECM, check again from step  1
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