Parts for your 2020 Subaru Impreza-Throttle position sensors

2020 Subaru Impreza throttle position sensor: what it is, where it lives, and how to look after it

Based on Subaru’s factory service information for the 2017–2021 Impreza with the FB20 engine (Throttle Control System in the Engine Diagnostics manual) and common OBD-II diagnostics for this model (DTCs such as P0121, P0122, P0123, P2135), the 2020 Subaru Impreza does use a throttle position sensor. It isn’t a separate bolt-on “TPS” like older cable-throttle cars, it’s built into the electronic throttle body as a redundant pair of sensors and is not serviced on its own. Subaru parts catalogues list the complete throttle body assembly as the service part when TPS faults are confirmed.

On this Impreza, the throttle position sensors tell the engine control module exactly where the throttle plate is, moment to moment. Working with the accelerator pedal position sensors, they let the ECU command the right amount of airflow for smooth take-offs, steady cruising, and clean idle. The ECU also leans on these signals to manage emissions, air-con load, cold starts, and the CVT’s drivability. Because it’s a drive-by-wire system, there are usually two internal position tracks for safety, and the ECU constantly checks they agree.

Routine servicing doesn’t include replacing the sensors, they’re sealed within the throttle body. What helps is keeping the intake system healthy so the sensors and throttle motor have an easy life. A fresh air filter, no vacuum leaks, solid battery voltage, and a clean throttle bore all make a difference. If cleaning, remove the throttle body and use a throttle-body-safe cleaner on the bore and plate. Don’t flood the electronics, don’t pry the blade open aggressively, and fit a new gasket on refit. Spraying cleaners blindly down the intake with it installed can wash residue into the motor and sensors—best avoided.

If diagnostics (live data, wiring checks, and correlation tests) point to a failed throttle body/TPS, replace the complete assembly with quality OEM-spec. After installation, clear codes and perform an idle/throttle relearn. A scan tool procedure is ideal, but the ECU will usually self-learn after the engine reaches operating temperature and idles for several minutes with all accessories off, followed by a short, gentle drive cycle with varied throttle. Always follow the torque specs and steps in the Subaru service manual.

• Common symptoms of TPS/throttle body issues: intermittent limp mode, erratic idle, hesitation, poor fuel economy, and the MIL on with TPS-related DTCs.
• Good prevention: keep the battery and grounds healthy, fix intake leaks promptly, and clean the throttle body at sensible intervals.

FAQs

Does the 2020 Subaru Impreza have a separate TPS I can replace?
No. The throttle position sensors are integrated into the electronic throttle body. If the TPS side fails testing, the fix is to replace the throttle body assembly. This design improves reliability and safety in drive-by-wire systems but removes the option of a cheap standalone TPS swap.

Do I need to do a relearn after replacing or cleaning the throttle body?
Yes. After replacement, perform a throttle/idle relearn with a capable scan tool if available. If not, many workshops let the engine reach full operating temperature and idle for several minutes with all loads off, then complete a short drive cycle with gentle accelerations. Even after a thorough clean, a brief relearn helps stabilise idle and throttle response.

Can cleaning fix TPS-related fault codes on this model?
If the codes are caused by a sticky plate or airflow mismatch, a careful clean can help. But correlation or circuit codes (like P2135 or persistent P0121–P0123) often indicate a sensor or wiring fault. Always confirm with live data and pin checks before calling the throttle body.