8 Symptoms of a Bad Throttle Position Sensor
Even if your car was running perfectly fine last time, it suddenly starts acting very strange. Your idle speed may fluctuate, your car may jerk while driving, or it may stall at traffic lights. The check engine light may also be on.
Even if you don’t have a code reader hooked up, you’re almost certain to have a problem with your throttle position sensor. Here we explain how the throttle position sensor (TPS) works, address the most common symptoms of a bad throttle position sensor, and give you an estimate of how much it might cost to replace it. Common Symptoms of a Bad Throttle Position Sensor
If your throttle position sensor is faulty, your engine control unit (ECU) will not be able to detect the throttle position. As a result, the engine control unit will not be able to properly regulate the amount of air entering the engine for successful combustion. This will ultimately reduce your drivability to the point where it is unsafe to stay on the road.
If your TPS is damaged or worn out, you may immediately notice a change in the way your car behaves. While you may not realize that the TPS is the root cause, if you have these symptoms, you should seek further evaluation or a professional diagnosis.
1) Check Engine Light
The throttle position sensor is a vital part of the entire combustion process. Ultimately, if this sensor is faulty, your engine will not be able to produce enough power to meet your acceleration needs.
If this problem is present, the engine control module will detect it and turn on the check engine light on your dashboard. This way, you know there is a problem with your engine that needs to be addressed.
The check engine light is one of the first signs of a bad throttle position sensor. This is because the TPS monitors the throttle position and passes this information to the engine control module. If the TPS malfunctions, it will send incorrect data (or not send it at all), which will cause problems with engine performance.
Common diagnostic trouble codes associated with the TPS are P0121, P0122, P0123, P0124, P2101, P2135, and P2138.
2) Weak Acceleration
If the throttle position sensor is defective, it can send a false signal that less power is required, even when you press the accelerator pedal firmly. This miscommunication results in poor fuel injection and ignition timing, sluggish acceleration, and poor overall engine performance. Of course, it also impacts fuel economy (see below).
3) Rough Engine Idling
When you stop your car or park it somewhere, the idle speed displayed on the tachometer on your dashboard should be between 600 and 900 rpm. If you notice that your engine speed drops below and above this range when your vehicle is stopped or parked, then you have a problem with a rough engine idle or speed fluctuations.
This is because a malfunctioning TPS can send inaccurate information about the throttle position, especially at idle. This causes the ECU to miscalculate the amount of fuel needed, resulting in an inaccurate air-fuel ratio.
As a result, the engine may receive too much or too little fuel, resulting in erratic operation or idling.
4) Excessive Fuel Consumption
Because the throttle position sensor has a large impact on the proper air-fuel mixture for combustion, an inaccurate reading can result in too much fuel being injected into the combustion chamber, resulting in a rich air-fuel ratio and reduced fuel economy.
Additionally, other sensors rely on accurate readings from the TPS. Even when that doesn’t happen, these sensors often compensate for too little or too much airflow. As a result, you may need to refuel more frequently than usual.
5) Unexpected Acceleration Changes
A defective TPS can send erratic signals to the engine controller, causing unexpected acceleration changes. This can cause sudden power spikes or slowdowns without the driver changing their accelerator pedal input. The engine may rev unexpectedly or the car may lose power temporarily.
6) Transmission Issues
Failure of the throttle position sensor can also affect the performance of an automatic transmission. The TPS helps determine when to change gears based on throttle position and engine load. A fault can send a false signal, causing the transmission to shift at the wrong time.
This not only affects driving comfort, but can also lead to increased wear on transmission parts. In some cases, the vehicle may go into “limp mode” as a protective measure, severely limiting the vehicle’s performance.
7) Car Won’t Start
In rare cases, a defective throttle position sensor can prevent the car from starting. The Engine Control Module (ECM) relies on input from the TPS to determine the correct amount of fuel to inject at start. Without this information, the ECM may not be able to initiate the start sequence or provide the correct fuel mixture, resulting in an engine that won’t start. You may hear the starter engage, but the engine will not start.
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.
