TPS sensor: how it works, how it fails, how to fix it
The throttle position sensor tells your engine computer how far the throttle is open. When it fails you get hesitation, surging, a bad idle or limp mode. Here is how to confirm it, fix it, and buy the right part without guessing.
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What a TPS sensor does
The short version, with the two drawings that explain nearly every TPS fault.
The throttle position sensor sits on the throttle body, on the end of the throttle shaft. It gets a 5 volt reference and a ground from the engine computer and returns a signal voltage that rises as the throttle opens. Code references cite roughly 0.5 volts at idle and 4.5 volts at full throttle as a typical pattern, but the exact numbers for your engine are in its service manual (OBD-Codes.com).
Classic sensors are a potentiometer: a wiper sliding along a resistive track. When the track wears, the signal drops out at one spot, and the engine stumbles there. Some sensors read a magnet with no contact at all (SMP listing).
On an electronic throttle, there is no cable. A motor opens the throttle, and two position signals inside the throttle body are compared constantly. When they disagree you get P2135 and usually reduced power.
TPS symptom checker
Tick what the vehicle is doing and any codes. You get the likely causes, ranked, with the next check for each. It is a guide, not a diagnosis.
Likely causes
Pick at least one symptom or code to see likely causes.
TPS trouble codes
Six generic OBD-II codes cover most throttle position faults. The last word of the title tells you where to look first.
Generic OBD-II throttle position codes. Titles from OBD-Codes.com; your maker may word them differently.
| Code | Generic title | In plain English | Guide |
|---|---|---|---|
| P0120 | Throttle Position Sensor/Switch A Circuit Malfunction | The signal is outside the range the computer expects. | P0120 guide |
| P0121 | Throttle Position Sensor/Switch A Circuit Range/Performance | The signal does not match what the engine is doing (RPM, airflow). | P0121 guide |
| P0122 | Throttle Position Sensor/Switch A Circuit Low Input | The signal voltage is too low, often an open or a short to ground. | P0122 guide |
| P0123 | Throttle Position Sensor/Switch A Circuit High Input | The signal voltage is too high, often a lost ground or a short to voltage. | P0123 guide |
| P0124 | Throttle Position Sensor/Switch A Circuit Intermittent | The signal drops in and out: wiring, a connector or a worn track. | Codes hub |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation | The two sensors in an electronic throttle body disagree. | P2135 guide |
Open the codes hub for P0124 and the first checks for every code.
Separate sensor, or built into the throttle body?
This one question decides what you buy and what it costs.
Cable throttle
A cable runs from the pedal to the throttle body. The TPS is usually a separate part on two screws. Some older ones are adjustable.
Electronic (drive by wire)
No cable; a motor moves the throttle. The sensors are usually inside the throttle body, so the fix is often a throttle body.
Buying a TPS sensor
Fitment beats brand. Match the part to your VIN or the number on your old sensor, then choose between OEM and aftermarket.
Who makes replacement throttle position sensors. No rankings: fitment matters more than the logo.
| Brand | What it is | Source | Shop |
|---|---|---|---|
| Standard Motor Products | Large aftermarket engine management maker. Some of its sensors are built to match OE output rather than being adjustable, and some read a magnet on the shaft with no contact. | Maker or listing page | Search Amazon |
| Delphi | Former GM parts arm with an aftermarket sensor line that includes throttle position sensors. | Maker or listing page | Search Amazon |
| Bosch | Says its aftermarket TPS is tested to the same standards as its original equipment parts (maker claim). | Maker or listing page | Search Amazon |
| Walker Products | Sensor and fuel system maker; describes its TPS as built for OE fit, form and function (maker claim). | Maker or listing page | Search Amazon |
| Dorman | Broad replacement parts catalog with TPS for GM, Dodge, BMW and many more. | Maker or listing page | Search Amazon |
| Hitachi (Astemo) | The former Hitachi Automotive, an OE supplier that sells TPS in the aftermarket. | Maker or listing page | Search Amazon |
| OEM (dealer) parts | ACDelco for GM, Motorcraft for Ford, Mopar for Jeep, plus Toyota and Honda genuine parts. Usually the priciest, always the exact match. | Dealer parts counter | Search Amazon |
We have not bench-tested these brands. Notes come from maker and distributor pages; maker claims are labeled. How we choose.
TPS by vehicle
The most-searched makes, with what is different about each and how to find the right part.
Every guide
Questions people ask
What does a TPS sensor do?
The throttle position sensor tells the engine computer how far the throttle is open. The computer uses it for fueling, idle control, and on many automatics, shift timing. Most send a voltage on a signal wire that rises as the throttle opens, from a 5 volt reference.
What are the symptoms of a bad TPS sensor?
Hesitation or stumbling when you press the gas, surging, a rough, low or racing idle, stalling, odd automatic shifts, reduced power on electronic throttles, and a check engine light with codes such as P0120 to P0124 or P2135.
Can I replace a TPS sensor myself?
On a cable throttle with a separate sensor, usually yes: a plug and two screws, then a check of the closed-throttle reading and any relearn your vehicle needs. On electronic throttles the sensors are usually inside the throttle body, which is a bigger job.
How much does it cost to replace a TPS sensor?
Published estimates for a separate sensor run roughly $120 to $355 at a shop, mostly labor. A sensor built into an electronic throttle body can mean $300 to $800 or more. See the cost guide for sources.
Is a TPS sensor the same as a tire pressure sensor?
No. TPS is the throttle position sensor on the engine. The tire pressure sensor is TPMS, fitted in each wheel. If the warning light on your dash is a tire symbol, you need a TPMS fix, not a TPS.