Parts for your 2004 Toyota Prius-Throttle position sensors

2004 Toyota Prius Throttle Position Sensor (TPS)

Yes, the 2004 Toyota Prius does use a throttle position sensor. It’s built into the electronic throttle body as part of Toyota’s ETCS-i (Electronic Throttle Control System – intelligent). The ECM compares the TPS signal with the accelerator pedal position sensors to control the throttle motor. Technical sources confirming this include: Toyota 2004 Prius Repair Manual (Engine Control System – SFI System, DTC P0120–P0124 for throttle/pedal position), Toyota New Car Features (NCF) for 2004 Prius describing ETCS‑i architecture, and the 2004 Prius Electrical Wiring Diagram showing the TPS integrated within the Throttle Body with Motor Assembly.

On a 2004 Prius, the throttle position sensor tells the engine computer exactly where the throttle plate sits, so it can balance driver demand, engine load, and hybrid system requests. Because this model is drive‑by‑wire, there’s no cable, the ECM drives the throttle motor and constantly cross‑checks two TPS signals (and two pedal sensors) for safety. If anything looks dodgy, it can drop into limp mode to protect the engine and hybrid system.

Most TPS issues on this car are flagged by fault codes like P0120–P0124 or P2135, uneven throttle response, stalling at stops, or the MIL coming on. A scan tool will show VTA1/VTA2 signals and throttle angle—techs look for smooth, linear changes and agreement between the two traces.

Worth noting: on the NHW20 Prius, the TPS isn’t a separate, bolt‑off sensor. It’s integrated into the throttle body, so the usual fix is to replace the Throttle Body with Motor Assembly if the TPS is faulty. Cleaning a gunked‑up throttle plate can help idle stability, but it won’t repair an internal sensor fault.

• Good servicing practice: periodically inspect the throttle body for carbon build‑up and clean with sensor‑safe throttle cleaner.
• Check the connector and loom for corrosion or damaged pins—water ingress or a poor earth can mimic a bad sensor.
• After throttle body replacement or battery disconnect, allow the ECM to relearn, using a proper scan tool (e.g., Techstream) to reset/initialise ETCS‑i is best practice.
• Use a new throttle body gasket, tighten evenly to spec, and avoid prying on the plate.

If the Prius is throwing TPS‑related codes, confirming the fault with data and wiring checks before replacing the assembly can save a few dollars in parts and labour. When in doubt, let a hybrid‑savvy technician handle it—there’s a bit of nuance in getting ETCS‑i happy again.

Popular questions about 2004 Toyota Prius throttle position sensors

Does a 2004 Prius actually have a TPS, or just a pedal sensor?

It has both. The 2004 Prius uses an accelerator pedal position sensor at the pedal and a dual‑channel throttle position sensor built into the throttle body. The ECM constantly compares them to manage the throttle motor safely and smoothly.

Can the TPS be replaced on its own, or is the whole throttle body needed?

On this model the TPS is integrated and not serviced separately. If the TPS has failed internal checks, the fix is typically replacing the Throttle Body with Motor Assembly, then performing the appropriate ETCS‑i reset/initialisation.

What’s the best way to diagnose a TPS problem on a 2004 Prius?

Scan for codes like P0120–P0124 or P2135, then view live data for VTA1/VTA2 and throttle angle. Look for smooth, matching traces. Inspect the connector and wiring, and rule out carbon‑sticking of the throttle plate. If signals are jumpy, mismatched, or out of range, the throttle body assembly may be due.