DTC B1500 Keyless UART Com. Malfunction: Wiring Diagram

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Keyless UART Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE CHART

Step	Check	Yes	No
1 CHECK DTC. Read the DTC of body integrated unit using Subaru Select Monitor. < Ref. to OPERATION , Read Diagnostic Trouble Code (DTC). >	Is B1500 current malfunction?	Go to step 2.	Go to step 7 .
2 CHECK DTC. Turn the ignition switch to OFF. Disconnect the connectors from body integrated unit and keyless entry control module. Connect the disconnected connectors. Turn the ignition switch to ON. Read the DTC of body integrated unit using Subaru Select Monitor.	Is B1500 current malfunction?	Go to step 3.	Go to step 7 .
3 CHECK HARNESS. Turn the ignition switch to OFF. Disconnect the connectors from body integrated unit and keyless entry control module. Using the tester, inspect the open circuit of harness and short (power supply-output short, GND-output short). Connector & terminal Keyless entry CM (i84) No. 24 - (R80) No. 3: TPMS & keyless entry CM (i84) No. 24 - (R221) No. 11:	Is harness normal?	Go to step 4.	Repair or replace the harness.
4 CHECK HARNESS. Using the tester, measure the voltage between keyless entry control module and chassis ground. Connector & terminal Keyless entry CM (R80) No. 4 (+) - Chassis ground (-): TPMS & keyless entry CM (R221) No. 6 (+) - Chassis ground (-):	Is the voltage battery voltage?	Go to step 5.	Check the power supply circuit for keyless entry control module.
5 CHECK HARNESS. Using the tester, measure the resistance between keyless entry control module and chassis ground. Connector & terminal Keyless entry CM (R80) No. 7 - Chassis ground: TPMS & keyless entry CM (R221) No. 5 - Chassis ground:	Is the resistance less than 10 Ω?	Go to step 6.	Repair the open circuit of harness or replace harness.
6 CHECK OPERATION. Install the keyless entry control module from other vehicle, which is working normally. Register the keyless key which is working normally. Operate the keyless key.	Is the door locking operate?	Replace the keyless entry control module. < Ref. to REMOVAL , Keyless Entry Control Module. >	Replace the body integrated unit. < Ref. to REMOVAL , Body Integrated Unit. >
7 CHECK CONNECTOR. Disconnect the connectors from body integrated unit and keyless entry control module.	Is there poor contact of connector?	Repair the connector, or replace harness.	Temporary poor contact occurs.