DTC U1674: Lin Communication Bus 2 Error Body Control Module

DTC detecting condition:

Integrated unit communication is shut down because of LIN error.

Trouble symptom:

LIN communication is not normal.

Wiring diagram:

Power window system Ref. to WIRING SYSTEM>POWER WINDOW SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to BODY CONTROL (DIAGNOSTICS)>General Description>CAUTION .

CHECK DTC .
1. Turn the ignition switch to OFF.
2. Turn the ignition switch to ON.
3. Wait for 5 seconds.
4. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to Body Control (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1674 displayed? (Current malfunction)

Yes: Go to 2 .

No: Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
CHECK CONTROL MODULE .
1. Turn the ignition switch to OFF.
2. Disconnect the power window main switch connector.
3. Turn the ignition switch to ON.
4. Wait for 5 seconds.
5. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to Body Control (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1674 displayed? (Current malfunction)

Yes: Go to 3 .

No: Replace the power window main switch. Ref. to GLASS/WINDOW/MIRRORS>POWER WINDOW CONTROL SWITCH .
CHECK CONTROL MODULE .
1. Turn the ignition switch to OFF.
2. Disconnect the front power window motor LH connector. (With the power window main switch connector disconnected)
3. Turn the ignition switch to ON.
4. Wait for 5 seconds.
5. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to Body Control (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1674 displayed? (Current malfunction)

Yes: Go to 4 .

No: Replace the power window motor LH. Ref. to GLASS/WINDOW/MIRRORS>FRONT REGULATOR AND MOTOR ASSEMBLY .
CHECK CONTROL MODULE .
1. Turn the ignition switch to OFF.
2. Disconnect the front power window motor RH connector. (With the power window main switch connector, front power window motor LH connector disconnected)
3. Turn the ignition switch to ON.
4. Wait for 5 seconds.
5. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to Body Control (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1674 displayed? (Current malfunction)

Yes: Go to 5 .

No: Replace the front power window motor RH. Ref. to GLASS/WINDOW/MIRRORS>FRONT REGULATOR AND MOTOR ASSEMBLY .
CHECK CONTROL MODULE .
NOTE: If auto function is equipped on front seats only, Go to 7.
1. Turn the ignition switch to OFF.
2. Disconnect the rear power window motor RH connector. (With the power window main switch connector, front power window motor LH connector, and front power window motor RH connector disconnected)
3. Turn the ignition switch to ON.
4. Wait for 5 seconds.
5. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to Body Control (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1674 displayed? (Current malfunction)

Yes: Go to 6 .

No: Replace the rear power window motor RH. Ref. to GLASS/WINDOW/MIRRORS>REAR REGULATOR AND MOTOR ASSEMBLY .
CHECK CONTROL MODULE .
1. Turn the ignition switch to OFF.
2. Disconnect the rear power window motor LH connector. (With the power window main switch connector, front power window motor LH connector, front power window motor RH connector, and rear power window motor RH connector disconnected)
3. Turn the ignition switch to ON.
4. Wait for 5 seconds.
5. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to Body Control (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1674 displayed? (Current malfunction)

Yes: Go to 7 .

No: Replace the rear power window motor LH. Ref. to GLASS/WINDOW/MIRRORS>REAR REGULATOR AND MOTOR ASSEMBLY .
CHECK HARNESS (OPEN CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the body integrated unit connector.
3. Measure the resistance between body integrated unit connector and each unit connector.
  Connector and terminal
  
  (i83) No. 2 - (Df34) No. 13:
  
  (i83) No. 2 - (Df52) No. 7:
  
  (i83) No. 2 - (Df51) No. 7:
  
  (i83) No. 2 - (Dr42) No. 7: (if auto function is equipped on rear seats)
  
  (i83) No. 2 - (Dr41) No. 7: (if auto function is equipped on rear seats)
Is the resistance less than 10 Ω?

Yes: Go to 8 .

No: Repair the open circuit of harness.
CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY) .
1. Turn the ignition switch to ON.
2. Measure the voltage between each unit connector and chassis ground.
  Connector and terminal
  
  (i83) No. 2 (+) - Chassis ground (-):
  
  (Df52) No. 7 (+) - Chassis ground (-):
  
  (Df34) No. 13 (+) - Chassis ground (-):
  
  (Df51) No. 7 (+) - Chassis ground (-):
  
  (Dr42) No. 7 (+) - Chassis ground (-): (if auto function is equipped on rear seats)
  
  (Dr41) No. 7 (+) - Chassis ground (-): (if auto function is equipped on rear seats)
Is the voltage less than 1 V?

Yes: Go to 9 .

No: Repair the short circuit to power supply in harness.
CHECK HARNESS (GROUND SHORT CIRCUIT) .
Measure the resistance between each unit connector and chassis ground.

Connector and terminal

(i83) No. 2 - Chassis ground:

(Df52) No. 7 - Chassis ground:

(Df34) No. 13 - Chassis ground:

(Df51) No. 7 - Chassis ground:

(Dr42) No. 7 - Chassis ground: (if auto function is equipped on rear seats)

(Dr41) No. 7 - Chassis ground: (if auto function is equipped on rear seats)

Is the resistance 1 MΩ or more?

Yes: Replace the body integrated unit. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>BODY INTEGRATED UNIT .

No: Repair the ground short circuit of harness.