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.

1. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Turn the ignition switch to ON.
   3. Wait for 10 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 code)

   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.
2. CHECK BODY INTEGRATED UNIT CUSTOMIZATION  .

   Using Subaru Select Monitor, make sure the [Customize] setting values to [Body Control] correspond to the vehicle.

   Is the setting value of [P/W ECU Setting] equal to [Driver/Passenger Seat]?

   Yes:  Go to  3.

   No:  Change the setting value to [Driver/Passenger Seat].

3. 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 10 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 code)

   Yes:  Go to  4.

   No:  Replace the power window main switch. Ref. to GLASS/WINDOWS/MIRRORS>POWER WINDOW CONTROL SWITCH .

4. CHECK CONTROL MODULE  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the front regulator & motor assembly (driver's side). (With the power window main switch connector disconnected)
   3. Turn the ignition switch to ON.
   4. Wait for 10 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 code)

   Yes:  Go to  5.

   No:  Replace the front power window motor (driver's side). Ref. to GLASS/WINDOWS/MIRRORS>FRONT REGULATOR AND MOTOR ASSEMBLY .

5. CHECK CONTROL MODULE  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the front regulator & motor assembly (passenger's side). (With the power window main switch connector and the front regulator & motor assembly (driver's side) connector disconnected)
   3. Turn the ignition switch to ON.
   4. Wait for 10 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 code)

   Yes:  Go to  6.

   No:  Replace the front power window motor (passenger's side). Ref. to GLASS/WINDOWS/MIRRORS>FRONT REGULATOR AND MOTOR ASSEMBLY .

6. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the body integrated unit connector.
   3. Using a tester, measure the resistance between the body integrated unit connector and each unit connector.

      Connector & terminal 

      (i361) No. 4 - (Df34) No. 17:

      (i361) No. 4 - (Df51) No. 7:

      (i361) No. 4 - (Df52) No. 7:

   Is the resistance less than 10 Ω?

   Yes:  Go to  7.

   No:  Repair the open circuit of harness.

7. CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY)  .
   1. Turn the ignition switch to ON.
   2. Using a tester, measure the voltage between each unit connector and the chassis ground.

      Connector & terminal 

      (i361) No. 4 (+) - Chassis ground (-):

      (Df34) No. 17 (+) - Chassis ground (-):

      (Df51) No. 7 (+) - Chassis ground (-):

      (Df52) No. 7 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes:  Go to  8.

   No:  Repair the short circuit to power supply in harness.

8. CHECK HARNESS (GROUND SHORT CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Using a tester, measure the resistance between each unit connector and the chassis ground.

      Connector & terminal 

      (i361) No. 4 - Chassis ground:

      (Df34) No. 17 - Chassis ground:

      (Df51) No. 7 - Chassis ground:

      (Df52) No. 7 - Chassis ground:

   Is the voltage 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.