Parts for your 2012 Toyota Prius-Throttle position sensors

2012 Toyota Prius throttle position sensor (TPS): purpose, care and when to replace

Yes, the 2012 Toyota Prius is fitted with a throttle position sensor. Technical sources confirm it’s part of Toyota’s ETCS-i (Electronic Throttle Control System – intelligent), integrated into the throttle body assembly alongside the throttle motor. The Toyota Repair Manual for the ZVW30 Prius lists TPS-related diagnostics (e.g., P0120–P0124, P2135), Toyota Techstream shows “Throttle Position Sensor No.1/No.2” data items, and the Toyota parts catalogue notes the sensor is not sold separately from the throttle body assembly (e.g., 22030-37010/37011).

On a 2012 Prius with the 1.8‑litre 2ZR‑FXE engine, the throttle position sensor tells the engine control module the exact angle of the throttle plate. Because the car is drive‑by‑wire, there’s no cable—just sensors and a motor. The TPS works in tandem with the accelerator pedal position sensors, providing two redundant signals so the hybrid system can command the right engine torque for smooth take‑offs, seamless engine start/stop, and decent fuel economy. The ECM watches the TPS constantly to fine‑tune fuel delivery, ignition timing and airflow, and to coordinate with hybrid functions like regenerative braking and idle‑stop.

There’s no scheduled replacement for the TPS on a Prius, and it’s not a separate bolt‑on part—if it fails, the fix is to replace the throttle body assembly. Signs it’s time for attention include a Check Engine light with TPS codes, erratic idle under the bonnet when the engine kicks in, surging, limp mode, or poor economy. Before calling time on the throttle body, a technician will often clean the throttle bore and plate (sensor-safe throttle body cleaner only), check the connector for corrosion, and inspect the harness where it bends near the unit. If the sensor output is jumpy or the two TPS signals don’t agree (often flagged as P2135), replacement is the reliable cure.

When fitting a new throttle body, always use a fresh gasket, manage any coolant hoses attached to the body, and ensure the connector seats firmly. After installation, perform ETCS initialisation with Techstream, if that’s not available, key ON (without starting) for about 30 seconds to let the ECM learn the fully closed position, then start and let it idle until warm. Following a battery disconnect, it’s normal for the ECM to relearn over a few kilometres. Keeping the intake clean and the electricals tidy helps the TPS live a long, drama‑free life.

• Common TPS trouble codes: P0121, P0122, P0123, P2135
• Best practice: clean throttle body during routine servicing, don’t spray cleaner into connectors
• Replacement: throttle body assembly (sensor is integrated)

Popular questions

Does a 2012 Prius have a throttle position sensor?
It does. The TPS is built into the throttle body with the throttle motor as part of Toyota’s ETCS‑i. It isn’t sold separately, so any TPS fault typically means replacing the complete throttle body assembly.

What are the symptoms of a failing TPS on a Prius?
Drivers might notice a Check Engine light, a lack of power or limp mode, surging or hesitation when the engine starts and stops, or worse fuel use. Diagnostic trouble codes like P0121–P0123 or P2135, and rough or inconsistent throttle readings in Techstream, point strongly at TPS issues.

Can it be driven with a bad TPS?
It may run, but it’s not wise. The hybrid system can limit power to protect itself, and the car may behave unpredictably. For safety and to avoid further damage, get it diagnosed and sorted promptly.