Your vehicle engine relies on thousands of components, and while many might get a great deal of attention, one that is often overlooked is your throttle position sensor (TPS).
The throttle body helps regulate fuel, monitoring the air entering your engine.
The data that the throttle position sensor collects provides the amount of air entering the engine continuously, as well as the precise amount of gas to inject into the engine at a given time.
When the throttle position sensor and all of its associated parts all do their job correctly, you’ll find that your vehicle accelerates, coasts, and cruises quite effectively while providing peak performance.
If the throttle position sensor fails, the signs of a bad throttle position sensor can be manifest as performance limitations, poor fuel economy, erratic idling, and many more.
What is a Throttle Position Sensor?
The throttle position sensor measures the position of the throttle valve, which is controlled by pressing the gas pedal down.
The throttle position also controls how much air is flowing into the engine intake; if the throttle is wide open, much air is flowing; if the throttle is nearly closed, only a little air is flowing.
The position of the throttle and the rate of closure is sent to the engine control module, along with other factors, to help the computer determine how much fuel is injected and the timing of the combustion event by determining how much air is injected.
The TPS is usually located on the throttle body.
When the throttle position sensor fails, it may cause the check engine light to come on, or the engine may idle roughly, surge, stall or hesitate because the engine control module does not know the position of the throttle and can not determine the correct fuel mixture or ignition timing.
Symptoms of bad throttle position sensor
Your vehicle has a variety of symptoms that will appear to indicate the driver of a failing, or defective, throttle position sensor.
Some of these symptoms can also a clogged throttle body symptom. While others indicate various other engine issues. But chances are if you are experiencing two or more of these symptoms, you have a bad throttle position sensor.
#1. Check engine light.
The throttle position sensor has a crucial duty in the internal combustion process. If this car sensor develops a failure, you will see a very serious poor engine performance and rough acceleration, in which case the ECU will recognize this fault, and illuminate the engine warning light on the dash. Then, you will know your engine has a fault needing attention.
#2. Car won’t accelerate or weak acceleration.
With a malfunctioning TPS, your vehicle may not accelerate as it should, and feels like it hesitates, jerks or doesn’t run smoothly at all. The vehicle engine may have good acceleration, but doesn’t have the engine power.
Alternatively, the vehicle throttle may seem to suddenly accelerate by itself while you are driving. You may experience this situation; if you are, there is a good chance it’s a problem with the throttle position sensor.
If this is true, the TCP will send a false signal to the ECM, which in turn cannot tell the engine when to operate correctly.
#3. Engine Rough Idling, Engine stalling, or idles too slowly.
You may be wondering, “does a bad throttle position sensor cause misfire?” If you notice your engine misfiring, or the engine is stalling, or the engine is rough idling when parked or when you stop, this could be an indication your throttle position sensor could be bad.
When you start your vehicle, and it idles, the RPM’s should be, between (600-900 RPM).
If your RPM’s go above or below that range you have erratic or rough idling problems, “If you notice this problem being a recurring issue, along with one or more problems on this list, this could be traced down to a bad throttle position sensor.”
#4. Excess gas consumption.
The throttle position sensor signals the proper air/fuel mixture for combustion. TPS issues will create a false signal that results in excess gas entering the cylinders and lead to Lean/rich fuel mixture issues and poor gas mileage.
The throttle position sensor works with other related sensor partners that rely on accurate signals from the throttle position sensor. If the TPS fails those sensors will provide inadequate air flow signals that will cause high gas consumption.
When experiencing excess gas consumption, be sure to check your vehicle 02 sensor as well. It plays a significant role in gas mileage.
#5. Automatic transmission problems.
You ask the question ‘can throttle position sensor affect transmission shifting?’ The answer is yes, of course! The throttle position sensor monitors the position of the acceleration in an engine controlled by the gas pedal located far right floor on the driver’s side.
It determines how much gas goes into the engine so it in turn determines engine load and controls the speed of the vehicle. When the throttle position sensor goes bad, it affects the automatic transmission and ultimately will cause hard-shifting.
#6. Car Accelerates fine but won’t shift up or exceed a certain low speed
Common TPS failure issue arises when it is no longer determining the adequate power requested by the gas pedal.
In this situation your vehicle will idle and accelerate nicely and smoothly, but won’t propel past a certain low-speed regardless of your acceleration request of fuel, which is around 25-35 MPH.
How do you diagnose a throttle body?
If you have a vehicle issue and you notice poor acceleration, or maybe it simply seems a little sluggish.
It doesn’t want to go when you push down on the accelerator pedal or if your engine is idling, your RPM or engine speed goes up and down – kind of an erratic idle; you’ve likely got a bad throttle body. I’m going to show you how to diagnose and repair a throttle body on a car or truck.
#1. Find the throttle body.
The first thing you want to do for the diagnosis is locate the throttle body. To do that, you will follow the air filter down the air duct to the engine. The throttle body is usually located in close proximity to the air intake.
As you may have spied, not all vehicles are the same. In older vehicles, the throttle bodies are typically part of the carburetor.
#2. Remove components that are blocking access to the throttle body.
The first thing to do is remove the air intake duct. So, loosen the fasteners with a screwdriver and get it out of the way. If there happen to be other components blocking access, you will have to loosen them up to get to it.
#3. Visually inspect the throttle body.
You will want to look in the throttle body and see if you can identify any dark areas that may look like carbon or some sort of debris.
Anything like that could cause the butterfly flap inside the throttle body to restrict some way and, of course, cause delayed acceleration when you push down the gas pedal.
#4. Inspect the electrical connectors.
With the electrical connectors unplugged, look inside and see if you have any corrosion or anything on both sides of the electrical connector.
Any corrosion in between the electrical connectors could cause some resistance toward anything; that could definitely cause an issue.
#5. Remove the throttle body from the vehicle.
Remove the throttle body from the vehicle by taking the correct socket set and ratchet handle out of the toolbox mechanisms and loosening the bolts that hold it there.
#6. Clean the throttle body.
Depending on how clogged up the throttle body is, just by looking at the front, you might think it is not in the worst shape, but the flip side might be different.
You will want to clean all the junk spots inside. When cleaning a throttle body, don’t use any sort of multi-purpose solvent. You should ensure you get the throttle body cleaner or carb and choke cleaner. Make sure it says the words carb and choke on it, or else it will not work.
Spray in the throttle body cleaner and wash the dead spot with light washing brushes.
#7. Reinstall the throttle body.
Coat the throttle body surface with a little sealer, and I would suggest a gasket maker; then, tighten down the bolts that hold it together. Reinstall anything you removed to gain access to the throttle body.
How to replace the throttle position sensor and the replacement cost
A vehicle engine needs the proper amount of air, just like it needs a specific amount of gas. If it doesn’t get the right amount of air to combust efficiently for a specific moment, it will hurt the combustion process.
This means you will experience engine power loss and possible other problems. You do not want to look past the problem’s cause. You want to diagnose the underlying problem using an automotive scan tool, seek help from your mechanic for a complete inspection.
If it is confirmed that the bad throttle position sensor (TPS) is the culprit, it must be replaced with a high-end sensor. Average costs for a throttle position sensor range from $89 – $170.
Service costs should be around $40 – $60 and the different parts will be in the range of $49 – $110. This is just an approximate price, and prices can vary a little higher or lower. You will save service costs and therefore labor costs if you do your own repairs.
Replacing the throttle position sensor is easy and a simple process. If you dig in to the use of your automotive scan tool and see any of these error codes; P0120, P0121, P0122, P0123, P0124, P2135, then this implies that the ECU has caught the TPS has a problem. Stay tuned, I am going to show you how to replace the throttle position sensor.
Things Needed:
- Flathead screwdriver
- 100 mm socket (optional)
- Ratchet handle
- Throttle position sensor
Unhook the negative battery terminal and find your sensor: You want to disconnect the negative battery terminal so you do not short circuit or create a fault code to your car computer. Then, find the throttle position sensor (TPS). It is normally mounted to the throttle body.
Remove the electrical connectors and unscrew the TPS: Gently unhook the electrical connectors of the sensor. It is pretty easy to remove. You simply press the tab on it, and wiggle it right off.
After you remove the electrical connector, find the bolts or screws that are holding the TPS to the throttle body, and very gently, loosen and take it off. You always want to compare old parts with new parts.
Install the new throttle position sensor: After you compare and conclude that they are the same part, you want to install it using reverse procedure starting with mounting the TPS on the throttle body and installing the electrical connector back to the TPS.
Anytime you remove electrical connectors like the TPS connector, always check the connectors for corrosion. Any corrosion in those areas can cause high resistance, and of course this can be an issue. Once you snap the electrical connector, you should hear a click sound.
Hook up the negative battery terminal and cross-check your installation: Head back to the battery and make sure the negative terminals are tight. Tighten any other items you removed to make way for the installation.
Start the vehicle and run it on idle and acceleration to see if your work has paid off. Depending on the vehicle, such as older model Ford rangers or Chevrolet Silverado/Tahoe, you may need to set the sensor manually.
However, most Japanese cars will adjust automatically for peak performance. Be sure to watch this video.
FAQs.
How do you test a throttle position sensor?
The throttle position sensor has three electrical contacts – the ground, variable output, and +12 volt input.
Remove the TPS connector, insert the alligator test lead into the right Jack on the meter, and turn the range switch to the 20k ohm scale or 20,000 ohms. Once the leads connected to the variable output, TPS ground wire, and +12 volt input, slowly move the butterfly flap in the throttle body from its closed to full open position, all while watching the readings.
The reading should slowly increase as the flap is moved to the open position and then correspondingly, as the flap is moved to the closed position, the reading should decrease. If the reading increases or decreases abruptly while the flap is moved, that will mean the TPS is bad and replace it.
How do you reset the throttle position sensor?
The easiest and simplest way to reset the throttle position sensor is to either unplug the engine control fuse for 5 minutes or remove the negative battery terminal.
Can a throttle position sensor cause transmission issues?
The TPS sets the position of the aileron attached to the gas pedal and the gas pedal is responsible for setting the engine load. A faulty TPS can cause hard shifting on a automatic transmission.
When should I clean the throttle body?
A throttle body is a crucial component in your car’s fuel system. Most times, these types of systems will be cleaned if they need to be serviced. Most time it is just carbon build up.
Slow acceleration, or stuttering engine, and a shaky feeling while driving or uneven acceleration is a sign you should clean and inspect the throttle body if the check engine light is on.
Should I clean or replace a throttle body?
Typically throttle bodies normally get cleaned rather than replaced entirely. But some other functioning related to the system components may need to be replaced.
When you see erratic idle and engine hesistation, or any signs once again of a bad throttle body, always verify the MAF sensor is working correctly as well as a MAF sensor could also causing the erratic idle and hesitation.
Final word
If you perform these replacement procedures or you call out for help, observing the aforementioned symptoms of a bad throttle position sensor will keep you from having to incur high replacement costs, fuel economy issues, limited acceleration, and idling issues.
Always suspect your throttle position sensor if you observe two or more signs occurring at the same time.