DTC U1673 Lin Communication Bus Error Body Control Module: Wiring Diagram

WARNING: This page is about a different car, the 2015 Subaru Outback and 2015 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: For the coupling connector, refer to "WIRING SYSTEM".

Sunroof Control System <Ref. to POWER TOP/SUNROOF (Legacy), POWER TOP/SUNROOF (Outback), Sunroof Control System.>
Power seat system <Ref. to POWER SEATS (Legacy), POWER SEATS (Outback), Power Seat System.>
Power rear gate system <Ref. to TRUNK, TAILGATE, FUEL DOOR (Legacy), TRUNK, TAILGATE, FUEL DOOR (Outback), Power Rear Gate System.>

Fig 1: LIN Communication Bus Error Body Control Module - Wiring Diagram
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTICS PROCEDURE

Step	Check	Yes	No
1 CHECK DTC . Turn the ignition switch to OFF. Turn the ignition switch to ON. Wait for 5 seconds. Read the DTC. <Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC) .>	Is DTC U1673 displayed? (Current malfunction)	Go to step 2 .	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 . Turn the ignition switch to OFF. Disconnect the power rear gate control module connector. Turn the ignition switch to ON. Wait for 5 seconds. Read the DTC. <Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC) .>	Is DTC U1673 displayed? (Current malfunction)	Go to step 3 .	Replace the power rear gate control module. <Ref. to POWER REAR GATE CONTROL MODULE , Power Rear Gate Control Module.>
3 CHECK CONTROL MODULE . Turn the ignition switch to OFF. Disconnect the power seat memory control module connector. (With the power rear gate control module connector disconnected) Turn the ignition switch to ON. Wait for 5 seconds. Read the DTC. <Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC) .>	Is DTC U1673 displayed? (Current malfunction)	Go to step 4 .	Replace the power seat memory control module. <Ref. to POWER SEAT CONTROL MODULE (SEAT WITH MEMORY FUNCTION) , REMOVAL, Power Seat System.>
4 CHECK CONTROL MODULE . Turn the ignition switch to OFF. Disconnect the sunroof unit connector. (With the power rear gate control module connector and power seat memory control module connector disconnected) Turn the ignition switch to ON. Wait for 5 seconds. Read the DTC. <Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC) .>	Is DTC U1673 displayed? (Current malfunction)	Go to step 5 .	Replace the sunroof unit. <Ref. to SUNROOF MOTOR .>
5 CHECK HARNESS (OPEN CIRCUIT) . Turn the ignition switch to OFF. Disconnect the body integrated unit connector. Measure the resistance between body integrated unit connector and each unit connector. Connector & terminal (i81) No. 18 - (R422) No. 10: (i81) No. 18 - (R155) No. 12: (i81) No. 18 - (R125) No. 11:	Is the resistance less than 10 Ω?	Go to step 6 .	Repair the open circuit of harness.
6 CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY) . Measure the voltage between each unit connector and chassis ground. Connector & terminal (i81) No. 18 (+) - Chassis ground (-): (R422) No. 10 (+) - Chassis ground (-): (R155) No. 12 (+) - Chassis ground (-): (i125) No. 11 (+) - Chassis ground (-):	Is the voltage less than 1 V?	Go to step 7 .	Repair the short circuit to power supply.
7 CHECK HARNESS (GROUND SHORT CIRCUIT) . Measure the resistance between each unit connector and chassis ground. Connector & terminal (i81) No. 18 - Chassis ground: (R422) No. 10 - Chassis ground: (R155) No. 12 - Chassis ground: (i125) No. 11 - Chassis ground:	Is the resistance 1 MΩ or more?	Replace the body integrated unit. <Ref. to REMOVAL , Body Integrated Unit.>	Repair the ground short circuit of harness.