Inspection steps

WARNING: This page is about a different car, the 2014 Subaru BRZ. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION:

Before measuring the resistance of CAN bus, turn the ignition OFF and leave the vehicle as is for at least one minute without operating keys, switches, and doors. Disconnect the battery and wait for another one minute or more.
If DTC related with CAN communication system is output, always start the troubleshooting according to the procedure described in "How to troubleshoot". (Refer to HOW TO TROUBLESHOOT )
When the repair is complete, follow DTC check procedure to confirm the same DTC does not recur.
DTC check procedure: wait 2 seconds or more after IG ON
After turning the ignition switch to OFF, you may have to wait for a while before disconnecting the battery terminals. Check appropriate precautions for battery terminal disconnection before proceeding. (Refer to WORKING PRECAUTIONS AND NOTES )
Before performing troubleshooting, check the fuse for this circuit.

NOTE:

Before disconnecting a connector, check for loose or unplugged connection by pushing back the connector case.
After disconnecting the connector, make sure that its terminal and the case have no damage, deformation, or corrosion.

Check for open circuit in CAN bus main line (Main line to the engine control computer)

Disconnect the battery ground terminal, and then disconnect the vehicle harness connector A33 from the engine control computer.

Measure the resistance between the terminals.

RESISTANCE

Inspection terminals	Inspection conditions	Standard value
A33-19 - A33-18	Disconnection of the battery ground terminal	114 to 126 Ω

NG: Repair or replace CAN bus main line or connector

Fig 1: Identifying Engine Control Computer Connector Terminals

Courtesy of SUBARU OF AMERICA, INC.

OK: Go to Next Step

Check the wiring harness and connector (Power supply system)
1. Check the power supply system of the engine control computer. (Refer to ECM POWER SUPPLY SYSTEM )
  NOTE: If no defect is found in the power supply system of the engine control computer, replace the engine control computer.
  
  NG: Repair or replacement of wiring harness or connector
  
  OK: Replacement of the engine control computer (Refer to REMOVAL )