Parts for your 2013 Subaru Impreza-Throttle position sensors

2013 Subaru Impreza throttle position sensor: fitted, what it does, and how to look after it

Based on Subaru’s factory service information for the 2012–2014 Impreza (GP/GJ, FB20), the model uses an electronic throttle control (“drive‑by‑wire”). In this setup, a throttle position sensor (TPS) is built into the throttle body alongside the throttle actuator motor, and the accelerator pedal has its own position sensors. Subaru diagnostic sections covering DTCs such as P0121, P0122, P0123 and P2135 describe the TPS and its circuits, and the parts catalogue lists the throttle body as a sealed assembly with the sensor integrated rather than a separate bolt‑on TPS. So yes, the 2013 Impreza does use a TPS, but it’s part of the throttle body assembly.

On a 2013 Subaru Impreza, the throttle position sensor tells the engine computer exactly how far the throttle plate has opened. Working hand‑in‑hand with the accelerator pedal sensors, it helps the ECU decide fuel and ignition timing, manages idle speed, and smooths out take‑off and gear changes. Because it’s a drive‑by‑wire system, accuracy is everything—if the ECU can’t fully trust the TPS signal, it can go into limp mode to protect the engine and drivetrain.

Servicing-wise, the TPS on this model isn’t a standalone replacement item—it’s integrated into the throttle body. The smartest maintenance step is to keep the throttle body clean. Under the bonnet, remove the intake duct and gently clean the throat and plate with a throttle‑body‑safe cleaner and a lint‑free cloth. Don’t force the plate open and don’t flood the electronics. After cleaning or battery disconnection, the ECU may need a brief idle relearn, a short warm idle and an easy drive usually lets it recalibrate, though a scan tool “throttle/idle learn” function is ideal.

If the car shows hesitation, uneven idle, surging, poor fuel economy, or a Check Engine Light with codes like P0121–P0123 or P2135, have a tech confirm the fault with live data. It’s worth checking the wiring and grounds first, as voltage drop or corrosion can mimic a bad sensor. If the TPS is confirmed faulty, the fix is to replace the complete throttle body assembly. Expect to fit a new gasket, mind the coolant hoses on the body (clamp or plug to minimise spills), top up coolant if needed, and torque the bolts to factory spec. Once fitted, clear codes and perform a throttle/idle relearn. Using quality OEM‑equivalent parts and keeping the throttle clean will help the Impreza run sweet as for many kilometres.

• Common symptoms: rough idle, flat spots, limp mode, high or hunting idle, CEL with P0121–P0123/P2135.
• Good habits: periodic throttle body cleaning, proper electrical checks, and relearn after service.

Does a 2013 Subaru Impreza have a separate TPS I can replace?
Not on this model. The TPS is built into the throttle body with the actuator motor, so it isn’t sold as a standalone sensor. If diagnostics point to a failed TPS (and wiring checks are good), the usual repair is replacing the entire throttle body assembly, fitting a new gasket, and carrying out an idle/throttle relearn with a scan tool if available.

What are the signs the TPS/throttle body is playing up on a 2013 Impreza?
Owners typically notice hesitation on take‑off, surging at steady speed, stalling or a hunting idle, and a Check Engine Light. Fault codes commonly include P0121–P0123 (TPS circuit range/performance/low/high) and sometimes P2135 (throttle/pedal correlation). A technician will verify by watching live data for erratic throttle angle versus pedal position and by checking wiring integrity.

Do I need to calibrate or relearn anything after cleaning or replacing the throttle body?
After cleaning, the ECU usually relearns on its own with a warm idle and a varied, gentle drive. After replacement, it’s best practice to use a scan tool to perform throttle/idle learn or clear memory, then let the engine idle without loads before a test drive. That helps stabilise idle speed and restores smooth throttle response.