Parts for your 2021 Lexus Is-Throttle position sensors

2021 Lexus IS throttle position sensors (TPS): what they do and how to look after them

Based on technical references, throttle position sensors are fitted and very much relevant to the 2021 Lexus IS. The Lexus/Toyota Technical Information System (TIS) repair manual for the IS (covering 8AR‑FTS, 2GR‑FKS and IS300h powertrains) describes the Electronic Throttle Control System (ETCS‑i) with dual throttle position sensors built into the throttle body assembly, alongside an accelerator pedal position sensor at the pedal. The same manuals list related DTCs such as P0120–P0124, P0220–P0222 and P2135 for TPS circuit range/correlation faults. Lexus’ Electronic Parts Catalogue also shows a “Throttle Body with Motor Assembly” that incorporates the TPS as a non‑serviceable component.

On the 2021 Lexus IS, the throttle position sensors quietly handle the hard yards under the bonnet. They track the exact angle of the throttle plate and feed that to the engine ECU so it can juggle fuel, ignition and idle speed, and even keep the gearbox shifts smooth. Because the IS runs drive‑by‑wire (ETCS‑i), it doesn’t rely on a cable, instead, the ECU compares the accelerator pedal signals with the two independent TPS signals inside the throttle body for accuracy and safety. If they don’t agree, it’ll trigger a fault and may drop into a limp mode to protect the engine.

There’s no routine replacement interval for the TPS on this model. As the sensors are integrated into the throttle body, any TPS failure normally means replacing the whole throttle body assembly. That said, sensible servicing goes a long way:

• Keep the throttle bore clean. A light clean with throttle‑body safe cleaner at major services can prevent sticky idle and erratic response. Don’t force the plate open or drown the electronics.
• If the check engine light pops up with codes like P0121, P0122 or P2135, get proper diagnostics done. Technicians will check live data for the two TPS signals (they move inversely and should track smoothly) and compare them to the pedal sensor.
• After throttle body replacement or a flat battery, perform the throttle/idle learn procedure. On many IS models this is best done with a scan tool to initialise ETCS‑i so idle and tip‑in feel are spot on.
• Inspect the connector and harness near the throttle body, heat and vibration can harden wiring over time.

Owners can expect long service life from the TPS on a 2021 IS if the intake stays clean and any warning lights are checked early. When replacement is needed, using a genuine throttle body with a fresh gasket and having the calibration completed will keep it driving beautifully across Aussie and Kiwi roads.

FAQs

Does the 2021 Lexus IS actually have a throttle position sensor?
Yes. It uses two TPS sensors integrated inside the electronic throttle body, working with the accelerator pedal sensors to manage ETCS‑i. The system is designed with redundancy so the ECU can validate signals and maintain safe operation.

Should the TPS be replaced during routine servicing?
No, it’s not a scheduled service item. The best practice is periodic throttle‑body cleaning and checking for diagnostic trouble codes if drivability concerns arise. If the TPS fails, the throttle body assembly is typically replaced and then initialised with a scan tool.

What are the signs of a failing TPS on a 2021 IS?
Common clues include a check engine light, rough or high idle, hesitant throttle, unexpected limp mode, or harsh shifts. Fault codes like P0121 or P2135 are typical. A workshop can confirm by reviewing live data for both TPS channels and comparing them with the pedal signals.