What Happens if You Disconnect Your Car’s Throttle Position Sensor?

The throttle position sensor (TPS) is one of many parts that work together to enable the engine to run. It must connect to the powertrain control module (PCM) to ensure its readings reach the computer. However, what happens when you unplug the throttle position sensor or when the sensor develops a problem that disconnects it? Can you still drive your vehicle?

What Happens if You Disconnect the Throttle Position Sensor?

Disconnecting the throttle position sensor will cut the PCM off from critical information it needs when setting the air-fuel mix. Since so many processes rely on the engine getting the right mixture of air and fuel, a disconnected sensor causes various problems that affect the vehicle’s performance.

A disconnected TPS shares many of its symptoms with a bad throttle position sensor. Dirt and physical damage can stop the sensor’s signals from reaching the PCM.

Here are the most common symptoms and issues that stem from disconnecting the throttle position sensor from the rest of the engine:

Electronic Throttle Control Warning Light Switches On

Your vehicle’s instrument panel contains many warning lights, including a warning light for the electronic throttle control (ETC). In some vehicle models, the ETC warning light is a lightning symbol on the dash.

The electronic throttle control monitors the throttle parts, such as the throttle position sensor. It activates the ETC warning light if the sensor gets disconnected or develops an issue.

Some vehicles might not have an ETC warning light. Instead, they will illuminate their check engine light to indicate issues like a disconnected throttle position sensor.

Erratic Engine Power

A disconnected throttle position sensor might cause the engine to generate the wrong amount of power in response to you stepping on the accelerator. Furthermore, your vehicle will generally enter limp mode, which restricts you from driving with much throttle.

The engine needs a steady supply of fuel to keep up its speed. Unfortunately, the fuel supply fluctuates if the throttle position sensor is disconnected because the PCM doesn’t know the position of the throttle plate. Without the readings from the detached sensor, the PCM cannot determine how much fuel it should send to the engine. It’s forced to guess and might send too little or too much fuel, which will alter the air-fuel mixture and change the amount of power generated.

Your vehicle will generally go into limp mode, restricting you from driving with a lot of throttle.

–Anthony Harlin, ASE Certified Master Automobile Technician

Engine Goes Into Safe Mode

When the PCM detects that the throttle position sensor has been disconnected, it might put your vehicle in safe mode. It will illuminate the associated warning light on the dashboard.

Also called limp mode, safe mode limits the engine’s performance. In limp mode, the engine can only produce a minimum amount of power and the transmission gets restricted to 2nd gear. Your vehicle’s speed slows to a crawl and can only be safely driven over short distances.

If the PCM puts your vehicle in safe mode, you must take it to the dealership or a certified auto repair shop to fix the problem and reset the computer. Unless you repair the issue that triggered safe mode, the PCM will continue to prevent the engine from operating normally.

Engine Shutdown

The PCM might turn the engine off if it detects a disconnected throttle position sensor. If it prevents you from starting your vehicle, you might as well call for a tow.

Problems Starting the Engine

Depending on your vehicle’s model and model year, the engine might have trouble starting if you cut off the throttle position sensor while it’s not running. In the worst-case scenario, the engine might not start, stranding your vehicle in its parking space.

Poor Fuel Efficiency

The PCM relies on the throttle position sensor to determine the amount of fuel to spray into the cylinders. Without the readings from the sensor, the computer must guess how much it should add.

Too much fuel added causes the engine to run rich. The unburned gasoline or diesel can escape combustion and enter the exhaust system. The catalytic converter and other exhaust emission control devices offer a partial solution. However, the rest exit your vehicle as emissions.

A disconnected throttle position sensor will reduce your vehicle’s fuel efficiency. You’ll drop by the gas station more often, leading to an increase in your fuel spending.

Engine Runs Lean

If the PCM doesn’t send enough fuel, it creates a lean air-fuel mix. The engine will run lean, leading to issues like reduced power, stalling, and difficulty in starting the vehicle.

Engine Runs Rich

Conversely, sending too much fuel will lead to the engine running rich. Your vehicle will produce more emissions and develop other issues like bad idling and soot buildup on the spark plugs that can damage the ignition parts.

What is the Throttle Position Sensor?

The throttle position sensor is either a potentiometer or Hall Effect sensor that measures where the throttle is at any given moment. It determines the extent of the throttle’s opening, which correlates to the volume of air entering the engine.

The sensor sends its readings on the throttle’s position to the PCM. Additionally, the throttle position sensor assists the PCM in figuring out the amount of fuel to send to the engine. The sensor shows the volume of air passing through the throttle body. Based on the throttle position readings, the injectors must spray enough fuel to mix with the incoming air, creating the appropriate air-fuel mixture that isn’t too lean or rich.

Can You Drive After Disconnecting the Throttle Position Sensor?

Don’t drive your vehicle if its throttle position sensor has been disconnected from the PCM. While you can often start the engine and drive without a connected sensor, the various engine problems make it much harder to control your vehicle. It can also cause more problems in the future if you ignore it instead of fixing it.

How Much is a Replacement Throttle Position Sensor?

Be prepared to pay anywhere between $10 and $600 for a throttle position sensor. Sold as an individual part or as part of a throttle position sensor kit, the part’s price tag can vary depending on factors like your vehicle’s details and the product’s brand.