8 Symptoms of a Bad Throttle Position Sensor
Though your car was running just fine the last time you drove it, it’s suddenly acting really strange. The idle may be surging, the car jerking while driving, and it might even stall out at a stop light. Your check engine light is probably on as well.
Without plugging in a code reader, it’s a good guess you’re having some sort of problem with the throttle position sensor. Here we go over how a throttle position sensor (TPS) works, go over the most common symptoms of a bad throttle position sensor, and provide some estimates on its replacement cost.
Common Symptoms of a Bad Throttle Position Sensor
If you have a bad throttle position sensor, then the engine control unit (ECU) will not know the position of the throttle. As a result, the engine control unit will not be able to properly regulate the amount of air that enters the engine so that a successful combustion can be made. This will ultimately impact your driving ability to the point where it is unsafe to stay on the road.
When your TPS is damaged or worn out, you’ll likely notice changes in your car’s behavior right away. While you may not recognize the TPS as the root cause, these symptoms should motivate to investigate further or get a professional diagnosis.
1) Check Engine Warning Light
The throttle position sensor is a key component of the overall internal combustion process. If this sensor goes bad, your engine will ultimately fail to produce sufficient power to accommodate your acceleration needs.
The engine control unit will detect this problem when it exists and then activate the Check Engine warning light on the dashboard. That way, you will be aware that your engine has some kind of problem that needs to be addressed.
A check engine light is one of the first signs of a faulty throttle position sensor. This is because the TPS monitors the throttle’s position and relays this information to the engine control unit. When the TPS malfunctions, it sends incorrect data (or no data), which in turn causes engine performance issues.
The car’s computer detects this inconsistency and triggers the check engine light to alert the driver of a potential problem requiring attention. Common diagnostic trouble codes related to the TPS include: P0121, P0122, P0123, P0124, P2101, P2135, and P2138.
2) Weak Acceleration
With a faulty throttle position sensor, it may incorrectly signal that less power is required, even when the accelerator pedal is firmly pressed down.
This miscommunication results in reduced fuel injection and ignition timing, leading to sluggish acceleration and overall poor engine performance. Naturally, fuel consumption is also affected (as explained below).
3) Engine Rough Idling
When you stop or park your vehicle somewhere, its idle RPM shown on the tachometer in your dash should be somewhere in the vicinity of 600 to 900 RPM.
This happens because when the TPS malfunctions, it may transmit inaccurate information about the throttle’s position, particularly at idle. This in turn causes the ECU to miscalculate the required fuel amount, leading to an improper air-fuel ratio.
As a result, the engine may receive too much or too little fuel, causing it to run unevenly or stumble at idle.
4) Excess Fuel Consumption
Since the throttle position sensor has a major effect on proper air/fuel mixture for burning, inaccurate readings can cause too much fuel to injected into the combustion chamber. This will cause a rich air/fuel ratio which will result in decreased fuel efficiency.
In addition, other sensors depend on accurate readings from the TPS. When that doesn’t happen, those sensors will often compensate for too little or too much airflow. The end result is usually the need to go fill up on gas more frequently than usual.
5) Unexpected Acceleration Changes
A malfunctioning TPS can send erratic signals to the engine control unit, causing unexpected changes in acceleration. This may result in sudden surges of power or drops in speed, even when the driver isn’t changing throttle input. The engine might rev unexpectedly or the car could lose power intermittently.
6) Transmission Issues
A faulty throttle position sensor can also affect automatic transmission performance. The TPS helps determine when it’s time to shift gears based on throttle position and engine load.
You might experience harsh or delayed shifts, unexpected downshifts, or the transmission staying in a lower gear longer than necessary. Not only does this affect driving comfort but can also cause increased wear on transmission components.
7) Car Won’t Start
In rare cases, a bad throttle position sensor can prevent your car from starting altogether. The engine control module (ECM) relies on input from the TPS to determine the correct amount of fuel to inject during startup. Without this info, the ECM may not initiate the starting sequence or provide the correct fuel mixture, making it impossible for the engine to turn over.
You might hear the starter motor engage, but the engine won’t catch. This symptom is often accompanied by other symptoms above including an illuminated check engine light.
8) Lack of Power When Towing
If you use your vehicle for towing, a faulty throttle position sensor can be particularly problematic. Towing requires precise control of the engine’s power output, which depends heavily on accurate throttle position information.
With a faulty TPS, the engine may not respond correctly to throttle inputs, especially under the increased load of towing. You might notice a major lack of power when trying to accelerate or climb hills while towing.
