DTC U1673: LIN Communication Bus 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: 

Sunroof control system Refer to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>SUNROOF CONTROL SYSTEM>WIRING DIAGRAM . Refer to WIRING SYSTEM (IMPREZA MODEL)>SUNROOF CONTROL SYSTEM>WIRING DIAGRAM .

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 5 seconds.
   4. Read the DTC of [Body Control] using the Subaru Select Monitor. Refer to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U1673 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.
2. CHECK HARNESS (OPEN CIRCUIT). 
   1. Turn the ignition switch to OFF.
   2. Disconnect the body integrated unit connector and the sunroof unit connector.
   3. Measure the resistance between body integrated unit connector and sunroof unit connector.

      Connector & terminal 

      (i81) No. 18 - (R55) No. 7:

   Is the resistance less than 10 Ω?

   Yes:  Go to  3.

   No:  Repair the open circuit of harness.

3. CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY). 

   Measure the voltage between body integrated unit connector and chassis ground.

   Connector & terminal 

   (i81) No. 18 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes:  Go to  4.

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

4. CHECK HARNESS (GROUND SHORT CIRCUIT). 

   Measure the resistance between body integrated unit connector and chassis ground.

   Connector & terminal 

   (i81) No. 18 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes:  Replace the body integrated unit. Refer to SECURITY AND LOCKS>BODY INTEGRATED UNIT .

   No:  Repair the ground short circuit of harness.