Throttle Position (TPS) Sensor
What it is
The throttle position sensor reports how far the throttle is open. On modern drive-by-wire engines it is built into the throttle body and is a safety-critical input.
What it does
It tells the computer your accelerator demand so it can set fuelling, idle and transmission shift points. A failing TPS causes hesitation, surging, erratic idle and, on drive-by-wire cars, limp mode — and it sets codes P0121–P0123.
Symptoms of failure
- Codes P0121, P0122 or P0123
- Hesitation or surging on acceleration
- Erratic or stuck idle
- Unexpected limp mode / reduced power
- Harsh or wrong automatic shifts
Common fault codes
Which vehicles need it
All electronically fuel-injected engines; drive-by-wire throttle bodies are standard on cars from the mid-2000s on.
Replacement cost
| DIY (part only) | $20–$150 |
|---|---|
| At a shop (parts + labor) | $120–$400 |
| Replacement interval | No set interval — replace on failure. On drive-by-wire engines the whole throttle body is usually replaced. |
| DIY difficulty | Easy (DIY) for a standalone TPS; throttle-body units may need a relearn |
| Recommended brands | Standard Motor Products, Bosch, Delphi, OEM |
Where to buy the part
We may earn a commission from purchases made through these links, at no extra cost to you.
Frequently asked questions
Can a bad throttle position sensor cause limp mode?
Yes. On drive-by-wire engines the computer will cut power and enter limp mode if the two TPS signals disagree, as a safety measure. A P0121–P0123 code with sudden power loss points to the TPS or throttle body.
Do I need to reset anything after replacing the TPS?
Often yes on drive-by-wire engines — they need a throttle/idle relearn so the computer learns the new closed and wide-open positions. A scan tool or a key-cycle procedure usually does it.