Parts for your 2012 Subaru Impreza-Throttle position sensors

2012 Subaru Impreza throttle position sensors: what they do and when to service them

Based on Subaru’s own technical literature, throttle position sensing is absolutely used on the 2012 Subaru Impreza. The 2012MY Impreza with the FB20 engine runs an Electronic Throttle Control (drive‑by‑wire) system, and the factory Service Manual identifies dual throttle sensors integrated into the throttle body, along with an accelerator pedal position sensor. The Diagnostics section lists related DTCs (such as P0120–P0123/P0221) for the throttle sensor circuit, and the Owner’s Manual references the Electronic Throttle Control warning light behaviour. Put simply, throttle position sensors are fitted, monitored by the ECM, and critical to how this model drives.

On this Impreza, the throttle position sensors live inside the electronic throttle body and report the exact opening angle of the throttle plate. The ECM continuously compares these signals with the accelerator pedal position, then adjusts throttle opening for smooth response, stable idle, cold starts, emissions control and fuel economy. If the sensor signals don’t line up, the car can drop into limp mode to protect the engine and drivetrain.

For servicing, it’s worth knowing the TPS on the 2012 Impreza isn’t a separate, adjustable part—it’s built into the throttle body. If the sensor fails testing or sets hard faults, the correct fix is typically to replace the complete throttle body assembly and then carry out the idle/ETC relearn procedure with a scan tool. A few practical tips help avoid trouble and keep things sweet:

• Keep the throttle body clean. Light deposits can upset airflow and skew sensor readings. Use throttle-body-safe cleaner with the battery disconnected.
• Scan live data. Check both throttle position signals and the accelerator pedal signals—on a healthy car they should track smoothly with no dead spots.
• Chase wiring first. Corroded pins or a loose connector at the throttle body or pedal can mimic a bad sensor.
• After cleaning or replacement, perform an idle relearn so the ECM can recalibrate the throttle angle at rest.

Common warning signs include erratic idle, stalling when coming to a stop, sluggish throttle response, and the CEL with codes in the P0120–P0220 range. Because the sensor is integral, DIY “adjustments” aren’t on the cards, replacement of the assembly is the reliable route. A quality workshop will confirm faults with a scan tool, check the loom, fit the new throttle body with fresh gasket, and complete the relearn so the Impreza drives as it should.

Popular questions about 2012 Subaru Impreza throttle position sensors

Where is the throttle position sensor on a 2012 Impreza?
It’s built into the electronic throttle body on the intake, not a separate bolt-on sensor. That assembly contains dual TPS tracks for redundancy. The accelerator pedal also has its own position sensor, but that’s a different component.

Do I need to calibrate anything after replacing the throttle body?
Yes. After fitting the new throttle body, an idle or throttle relearn should be performed with a suitable scan tool. This teaches the ECM the exact closed position and ensures a stable idle and clean take-off.

What symptoms point to a failing throttle position sensor on this model?
Look for a check engine light with codes like P0121, P0122 or P0221, a hunting or high idle, hesitation on acceleration, or the car going into limp mode. Always rule out wiring or a dirty throttle plate before condemning the sensor.