Diagnostic Procedure

WARNING: This page is about a different car, the 2013 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK DTC. Read all DTCs using the Subaru Select Monitor.< Refer to OPERATION , Subaru Select Monitor. >	Is there DTC U1202?	Perform the diagnosis according to DTC.	Go to step 2 .
2 CHECK DTC. Read the DTC of body integrated unit using Subaru Select Monitor.	Is U1221 a current malfunction?	Go to step 3 .	Go to step 8 .
3 CHECK DTC. Turn the ignition switch to OFF. Disconnect all control module connectors (B280, B310, B55, B136, B230, B231) that are connected to high speed CAN communication line. Connect the disconnected connectors. Turn the ignition switch to ON. Read the DTC of body integrated unit using Subaru Select Monitor.	Is U1221 a current malfunction?	Go to step 4 .	Go to step 8 .
4 CHECK CURRENT DATA. Turn the ignition switch to OFF. Disconnect all control module connectors (B280, B310, B55, B136, B230, B231) that are connected to high speed CAN communication line. Using the tester, check for open, short (power supply-output short, GND-output short) in the harness. Connector & terminal (B40) No. 6 - (B136) No. 17: (B40) No. 6 - (B310) No. 35: (B40) No. 6 - (B230) No. 2: (B40) No. 6 - (B231) No. 2: (B40) No. 6 - (B55) No. 18 (AT model): (B40) No. 6 - (B280) No. 3:	Is harness normal?	Go to step 5 .	Repair or replace the harness.
5 CHECK HARNESS. Using the tester, check for open, short (power supply-output short, GND-output short) in the harness. Connector & terminal (B40) No. 14 - (B136) No. 28: (B40) No. 14 - (B310) No. 10: (B40) No. 14 - (B230) No. 3: (B40) No. 14 - (B231) No. 1: (B40) No. 14 - (B55) No. 17 (AT model): (B40) No. 14 - (B280) No. 9:	Is harness normal?	Go to step 6 .	Repair or replace the harness.
6 CHECK DTC. Turn the ignition switch to OFF. Connect the disconnected connectors. Start the engine and stop. Turn the ignition switch to ON. Read the DTC of body integrated unit using Subaru Select Monitor.	Is U1221 a current malfunction?	Go to step 7 .	Go to step 8 .
7 CHECK DTC. Read all DTCs using the Subaru Select Monitor.	Are DTCs P1718 or C0047 detected?	Replace the ECM.< Refer to REMOVAL , Engine Control Module (ECM). >	Replace the body integrated unit.< Refer to REMOVAL , Body Integrated Unit. >
8 CHECK HARNESS. Turn the ignition switch to OFF. Shake the harness used for CAN communication circuit. Turn the ignition switch to ON. Read the DTC of body integrated unit using Subaru Select Monitor.	Is U1221 a current malfunction?	Repair or replace the harness.	Go to step 9 .
9 CHECK CONNECTOR. Turn the ignition switch to OFF. Disconnect all the connector that is connected to high speed CAN circuit.	Is there poor contact of connector terminal?	Repair the connector terminal where poor contact exists, or replace harness.	Temporary communication failure occurs.