Parts for your 2019 Subaru Impreza-Throttle position sensors

2019 Subaru Impreza Throttle Position Sensor (TPS)

Based on Subaru technical documentation, the 2019 Subaru Impreza (FB20 engine) does use a throttle position sensor, but it’s built into the electronic throttle body rather than being a separate, bolt-on sensor. The Subaru Factory Service Manual (ETC/Engine Control sections) references TPS signals and related DTCs (e.g., P0121–P0123, P0221–P0223, P2135), and Subaru parts catalogues list the throttle body as a complete assembly with the motor and throttle sensor integrated. There’s also a separate dual Accelerator Pedal Position Sensor (APPS) at the pedal. That means TPS is absolutely relevant on this model, just not serviced as an individual sensor.

On a 2019 Subaru Impreza, the throttle position sensor’s job is to tell the engine control module exactly how far the throttle plate is open. That live feedback lets the car sort fuelling, spark timing, CVT shift strategy, cruise control and even stability control behaviour. Because it’s a drive-by-wire setup, the TPS lives inside the throttle body alongside the throttle motor, while the pedal has its own position sensors to confirm driver demand.

There’s no scheduled replacement interval for the TPS on this model. In practice, it’s “no-service” unless a fault is confirmed. If the ECU logs TPS-related codes or the data doesn’t track smoothly, the fix is typically to replace the complete throttle body assembly and fit a new gasket. After refitting, a throttle/idle relearn should be performed with a capable scan tool. If that’s not available, a drive cycle can let the ECU relearn, but a proper scan-tool routine is quicker and cleaner.

• Common symptoms: erratic idle, poor fuel economy, dead spot on acceleration, limp mode, and the MIL on with codes like P0121 or P2135.
• Cleaning: light throttle-body cleaning can help sticky operation, but never force the plate by hand and avoid soaking electronics. Use throttle-safe cleaner and keep overspray away from the MAF.
• Checks: compare live data for Accelerator Pedal Position and Throttle Position, they should correlate smoothly with no spikes or flat spots. Inspect wiring and grounds before condemning the unit.

1. If replacement is required, swap the throttle body assembly, fit a new gasket, and torque to spec.
2. Perform throttle/idle relearn with a scan tool, battery disconnect alone doesn’t guarantee proper calibration.
3. Road test and confirm stable idle, smooth throttle response, and no returning DTCs.

Day to day, keeping the air filter fresh, the intake tract sealed, and the battery/charging system healthy goes a long way to preventing nuisance TPS faults on the Impreza.

FAQs

Does the 2019 Subaru Impreza have a separate throttle position sensor?
It doesn’t. The TPS is integrated into the electronic throttle body with the throttle motor. The accelerator pedal has its own dual position sensor, but the throttle plate angle feedback (TPS) is part of the throttle body assembly and isn’t serviced separately.

How is a faulty TPS diagnosed on this model?
A technician will scan for codes like P0121–P0123 or P2135, then watch live data to see if Throttle Position tracks Accelerator Pedal Position smoothly. They’ll also check for wiring/connector issues and intake air leaks. Old-school resistance checks aren’t useful here because the sensor is internal and the system expects specific correlated signals.

Do you need a relearn after throttle body replacement or cleaning?
Yes. A throttle/idle learning procedure with a compatible scan tool is recommended after replacing the throttle body and often after deep cleaning. Without a relearn, the idle can be high, low, or unstable until the ECU slowly adapts, if at all.