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 STIFACTORY OEM SERVICE PROCEDURE
Diagnostic Method
Judge as NG when one of the following conditions is established.
JUDGMENT VALUE SPECIFICATION
| Malfunction Criteria | Threshold Value |
|---|---|
| (1) Absolute value monitoring A/D voltages for monitoring or A/D voltages for monitoring |
> 2.7 V < 2.5 V |
| (2) A/D/changes monitoring |(Buffer voltage of AD changes - base voltage of A/D changes)| |
> 0.029296875V |
| (3) A/D voltages for monitoring | Did not change |
| (4) |(Throttle position sensor (Main) - (amplified throttle position sensor (Main))/4)| | ≥3° |
| (5) (Amplified throttle position sensor (Main))/4 | ≤23.8235° |
Time needed for diagnosis:
- 200 ms
- 200 ms
- 200 ms
- 24 ms
- 24 ms
Malfunction indicator light illumination: Illuminates as soon as a malfunction occurs.
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.