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>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 CONTROL MODULE  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the sunroof unit 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. Refer to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U1673 displayed? (Current malfunction)

   Yes:  Go to  3.

   No:  Replace the sunroof unit. Refer to SUNROOF/T-TOP/CONVERTIBLE TOP (SUNROOF)>SUNROOF MOTOR .

3. 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 sunroof unit connector.

      Connector & terminal 

      (i83) No. 18 - (Rf22) No. 11:

   Is the resistance less than 10 Ω?

   Yes:  Go to  4.

   No:  Repair the open circuit of harness.

4. CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY)  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between the sunroof unit connector and chassis ground.

      Connector & terminal 

      (Rf22) No. 11 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes:  Go to  5.

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

5. CHECK HARNESS (GROUND SHORT CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Measure the resistance between the sunroof unit connector and chassis ground.

      Connector & terminal 

      (Rf22) No. 11 - Chassis ground:

   Is the resistance 1 MΩ or more?

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

   No:  Repair the ground short circuit of harness.