2018 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE

Diagnostic Trouble Code (DTC): List

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.
DTC Description & trouble part Reference
B1A00 FRONT RELAY CONTROL MODULE NON-VOLATILE MEMORY Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A00 FRONT RELAY CONTROL MODULE NON-VOLATILE MEMORY 
B1A01 FRONT RELAY CONTROL MODULE BATTERY (CONTROL) POWER SUPPLY Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A01 FRONT RELAY CONTROL MODULE BATTERY (CONTROL) POWER SUPPLY 
B1A02 FRONT RELAY CONTROL MODULE BATTERY (BUCK UP) POWER SUPPLY Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A02 FRONT RELAY CONTROL MODULE BATTERY (BUCK UP) POWER SUPPLY 
B1A03 FRONT RELAY CONTROL MODULE IG POWER SUPPLY Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A03 FRONT RELAY CONTROL MODULE IG POWER SUPPLY 
B1A04 HEAD LAMP LO LH CIRCUIT CURRENT HIGH Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A04 HEAD LAMP LO LH CIRCUIT CURRENT HIGH 
B1A06 HEAD LAMP LO RH CIRCUIT CURRENT HIGH Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A06 HEAD LAMP LO RH CIRCUIT CURRENT HIGH 
B1A08 HEAD LAMP HI LH CIRCUIT CURRENT HIGH Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A08 HEAD LAMP HI LH CIRCUIT CURRENT HIGH 
B1A0A HEAD LAMP HI RH CIRCUIT CURRENT HIGH Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A0A HEAD LAMP HI RH CIRCUIT CURRENT HIGH 
B1A0C FRONT RELAY CONTROL MODULE CAN REGISTER STUCK Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1A0C FRONT RELAY CONTROL MODULE CAN REGISTER STUCK 
U0074 CONTROL MODULE COMMUNICATION BUS "BODY-CAN" OFF Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC U0074 CONTROL MODULE COMMUNICATION BUS "BODY-CAN" OFF 
U0122 LOST COMMUNICATION WITH VEHICLE DYNAMICS CONTROL MODULE Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC U0122 LOST COMMUNICATION WITH VEHICLE DYNAMICS CONTROL MODULE 
U0140 LOST COMMUNICATION WITH BODY CONTROL MODULE Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC U0140 LOST COMMUNICATION WITH BODY CONTROL MODULE 
U0416 INVALID DATA RECEIVED FROM VEHICLE DYNAMICS CONTROL MODULE Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC U0416 INVALID DATA RECEIVED FROM VEHICLE DYNAMICS CONTROL MODULE 
U0422 INVALID DATA RECEIVED FROM BODY CONTROL MODULE Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC U0422 INVALID DATA RECEIVED FROM BODY CONTROL MODULE 
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.