Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2021 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE
Instrumentation System (Diagnostics)
- Basic Diagnostic Procedure
- Check List for Interview
- General Description
- Electrical Component Location
- Control Module I/O Signal
- Subaru Select Monitor
- Read Diagnostic Trouble Code (DTC)
- Clear Memory Mode
- Inspection Mode
- Read Current Data
- System Operation Check Mode
- User Customizing
- List of Diagnostic Trouble Code (DTC)
- Diagnostic Procedure with Diagnostic Trouble Code (DTC)
- DTC U0073: Control Module Communication Bus Off
- DTC U0100: Lost Communication With ECM/Pcm "A"
- DTC U0101: Lost Communication With TCM
- DTC U0122: Lost Communication With Vehicle Dynamics Control Module
- DTC U0128: Lost Communication With Park Brake Control Module
- DTC U0131: Lost Communication With Power Steering Control Module
- DTC U0140: Lost Communication With Body Control Module
- DTC U0151: Lost Communication With Restraints Control Module
- DTC U0156: Lost Communication With Information Center "A"
- DTC U0164: Lost Communication With HVAC Control Module
- DTC U0181: Lost Communication With Headlamp Leveling Control Module
- DTC U0327: Software Incompatibility With Vehicle Security Control Module
- DTC U1135: Lost Communication With DCCD Control Module
- DTC U1232: Lost Communication With Rear/Side Radar Control Module
- DTC U1235: Lost Communication With Eyesight
- DTC U1433: Invalid Data Received From Eyesight
- DTC U1533: Invalid Data Received From Rear/Side Radar Control Module
- DTC B1500: Fuel Sender Open/Short-Circuit Detection
- DTC B1501: Power Supply System Error Detection
- DTC B1507: External Air Temperature Open/Short Circuit Detection
- Diagnostics with Phenomenon
Factory Service Tools
Use the Manual With the Right Hardware
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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.