Throttle Position Sensor is a device found in almost all vehicles that have been designed to report the current position of the throttle body valve to the vehicle’s computer (ECU).
In this article, we’ll review the basics of a TPS, the symptoms of a faulty TPS, and its importance in engine performance.
What Is a Throttle Position Sensor
The Throttle Position Sensor (TPS) is an electronic device found in most modern vehicles that measure the position of the throttle valve so that the vehicle’s computer knows how much air is flowing in.
To get the best performance, the engine has to have the right mix of fuel and air in the combustion chamber. The computer that calculates how much fuel to put in needs to know how much air is going into the motor.
So, one of the sensors that the ECU uses to measure the air going in is the TPS. It actually tells the ECU how far the throttle is open.
The TPS helps the engine control system adjust air/fuel ratio, ignition timing, and other aspects of engine performance to provide optimal power output and fuel efficiency. It also allows for smoother operation when accelerating or decelerating.
The way that the ECU knows the position of the throttle valve is due to the potentiometer found in the throttle position sensor. This potentiometer is connected to the ECU by a resistive wire. When you press the gas pedal, the throttle valve opens up and the position sensor detects that and moves.
Now, the movement of the TPS (the potentiometer) is going to cause a voltage change and the ECU is going to measure that voltage change and will know the exact position of the throttle valve.
The ECU uses the TPS reading for:
- Traction control
- ABS
- Fuel injectors
- Cruise control
(See also: The 7 Best Throttle Body Cleaner Alternatives)
What Happens When Throttle Position Sensor Goes Bad
When the throttle position sensor goes bad you will notice a harder delayed shift because the ECM can’t communicate the position of the throttle body plate effectively to the TCM to make the shift at the perfect time.
Here is everything that can happen when the TPS goes bad:
Ignited check engine light
When the TPS goes bad, the ECU will trigger a check engine light with P0120, P0121, P0122, P0123, or P0124 trouble codes. These trouble codes are associated with a malfunction of the TPS. They can be read by using an OBD-II scanner.
Shifting problems
When the throttle position sensor goes bad, the driver will experience a shifting problem. This is because the faulty TPS isn’t able to report the position of the throttle valve in real-time and the engine has no data on how much air is in the combustion chamber. As a result, the ECU and the TCM are not communicating properly and the vehicle will not shift at the correct time.
Poor acceleration
When the TPS goes bad, the vehicle will have poor acceleration because the throttle position sensor isn’t communicating the exact position of the throttle plate to the ECM and prevents it from making the correct fuel adjustments which results in poor acceleration.
Limp mode
When the throttle position sensor goes bad, the vehicle can go into limp mode. Because the TPS is designed to measure the position of the throttle body and notify the ECU, when it goes bad, the vehicle will be stuck between the second and third gear with reduced power.
The limp mode is a safety feature that gets activated to protect the driver and the vehicle. In this case, the limp mode is activated to protect the vehicle from high RPMs that can lead to premature wear.
(See also: How To Clean a Throttle Body Without Removing It)
How Do I Know If My Throttle Position Sensor Is Bad?
- The car won’t accelerate or lacks power when accelerating
- Rough idle or stalls (sudden drop in RPMs)
- The car may accelerate but won’t go over the third shift
- Illuminated check engine light with P0120, P0121, P0122, P0123, or P0124 trouble code
- Sudden deceleration while cruising at a steady speed
- The vehicle will start burning more gas
What Causes The Throttle Position Sensor To Go Bad?
- Bad or burnt fuse
- A melted resistive wire that runs through the TPS
- A broken electrical connector
- High current running to the TPS
- Oil or other liquid leaking on the TPS
- Wear-and-tear
Can I Drive With a Bad Throttle Position Sensor?
You can drive with a bad throttle position but the vehicle will have shifting problems, poor acceleration, rough idle, and may go into limp mode and completely shut down. Depending on how bad the throttle sensor (TPS) is, you may be able to drive your vehicle to the repair shop.
Driving with a bad throttle position sensor can eventually lead to serious engine and transmission damage. This comes from the inability of the TPS to report the correct position of the throttle body valve which results in high RPMs, stuck between the second and third shift, and improper combustion which leads to an engine misfire.
Can a Throttle Position Sensor Be Cleaned?
Yes. A throttle position sensor can be cleaned simply by removing it and spraying it with a carburetor cleaner. Since the TPS doesn’t get dirty too often, you can clean it at least once a year as preventive maintenance.
Here is how to clean the throttle position sensor:
- Park the vehicle and open the hood.
- Locate the TPS. It is attached to one side of the throttle body.
- Gain access to the throttle body. This may include removing the air filter box (if it’s in the way).
- Disconnect the socket that feeds electrical power to the TPS.
- Remove the screws that are holding the TPS in place.
- Spray a carburetor cleaner directly onto the TPS spring. Do not get the electrical socket wet.
- Let the TPS dry completely.
- Reinstall the TPS.
In Conclusion
A throttle position sensor (TPS) is a device designed to measure and report the position of the throttle body valve in real time. This information goes to the vehicle’s computer (ECU). From there the ECU knows how much air is in the system so it can adjust the fuel injection.
If your vehicle has a faulty TPS, take your car to the repair shop as soon as possible. The shop may clean or replace the TPS. However, do not ignore this problem. A faulty TPS can lead to engine damage and high repair bills.