How to Tell Which Tire Sensor is Bad?

Published: 06/20/22 •  8 min read

You just got your car tires inflated. After you leave the mechanic’s shop, you notice a TPMS warning light blinking on your dashboard.

You get to know that one of the tire’s sensors is bad.

But you are confused, and cannot figure out which of the tire’s sensors is faulty.

So, to find out which of the tire’s sensors is bad, you can use one of the three methods.

The easiest way to locate the faulty sensor is by using diagnostic scan tools, which will report the errors in the TPMS system. The bad sensor can also be traced by comparing the readings of a digital pressure gauge with the sensors’ reading. Thirdly, you can try inflating and deflating the car’s tires, and figure out which of the wheels has bad sensors.

Now, before we get into the details of these methods, first you need to understand how the Tire Pressure Monitoring System (TPMS) works and what is the role of the pressure sensor in it.

How does the Tire Pressure Monitoring System work?

The tire pressure monitoring system (TPMS) has been an essential component of automobiles since 2008 when the US declared it mandatory for all vehicles.

This system is responsible for monitoring the pressures of all four tires of the car. It contains battery-powered pressure sensors on each tire which send the information to Engine Control Unit (ECU), and then the tire’s pressure information is displayed on the dashboard.

The ECU is programmed to give you a warning if any tire’s pressure drops 25% below the recommended value.

You might think that the pressure sensor directly measures the pressure inside each tire. The interesting part is that not all types of pressure sensors measure the pressure directly.

One type of pressure sensor does measure the direction with the help of a gauge mounted inside the tire.

However, some sensors measure the pressure indirectly. Do you know how?

Since the main purpose of the TPMS is to warn you if one or more tires are under-inflated. That job can be done without actually determining the pressure. So, in the indirect-TPMS, ECU takes information from the car’s ABS and calculates the difference in speeds of the tires.

A tire that is underinflated, is smaller in size, so it rotates faster compared to the one, which is properly inflated. So, if the ECU notes any difference in the rotational speeds, that means one of the tires has lesser pressure. When that happens, you notice a warning light on the dashboard.

The next possible query asked by most people is how do we know when there is a flaw in the TPMS.

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So, let’s talk about the possible symptoms you see when the tire’s pressure sensor is bad.

Symptoms of Bad Tire Pressure Sensor

The symptoms of a bad pressure include an illuminated TPMS or ABS warning light, shaky steering, increased fuel consumption, and incorrect warnings.

TPMS Warning Light

Whenever the car’s ECU finds about the tire pressure sensor is at fault, then it sends TPMS an error message, which is displayed on the dashboard screen. The TPMS warning light also gets illuminated.

ABS Light Illumination

If your car comes with an indirect pressure monitoring, then the illumination of the ABS lights may indicate that something is wrong with the sensor.

Steering Pulls on Sides

The four tires keep the car balanced and aligned. If one of the tires has low air pressure, the car’s alignment is disturbed. This makes driving difficult.

For instance, if the front tires have low air pressure, their sides become softer. This makes it hard for the driver to keep the steering wheel straight and steady.

If the steering pulls on sides but the TPMS doesn’t warn you about low pressure, that means one of its sensors has failed.

Increased Fuel Consumption

Driving with a tire that has very low air pressure or is nearing to become flat causes the car’s fuel consumption to increase.

More friction is produced, when you drag the car with a low-pressure tire. The engine needs to do more work to overcome this amount of friction. For that, it burns more fuel,

So, if you notice that your car’s fuel consumption has increased, get your tire’s pressure checked. Low pressure in the tires gets unnoticed if the sensor monitoring it fails.

Incorrect Warnings

The sensors in the TPMS measure the tires’ pressure continuously. A faulty sensor will send the incorrect information to ECU. As a result, you may see incorrect warnings and alerts on the screen.

For instance, the sensor may send a signal that the tire has very low pressure. But when you check, the tire’s perfectly inflated. Or tire has very low pressure, but the sensor says it is completely fine.

Once you find out that one or more tire sensor is not working. The next thing to figure out is which one?

How to find which tire sensor is bad? [3 Quick Ways]

You can find out about the bad tire’s sensor by using one of the three methods discussed. Use the one which is feasible for you.

Method #1: Diagnostic Tools

A faulty sensor may illuminate a warning light in the dashboard and show some error code. To read these error codes, you can use an OBD2 (Onboard Diagnostic II) scanner.

In addition, multiple diagnostic scan tools are available in the market that can communicate with engine ECU and the flaw in the TPMS can be traced.

However, using these tools may be difficult for a layman, so it is better to seek professional help for using these tools.

Method #2: Digital Pressure Gauge

An easy method for tracing which one of the tire sensors is bad is by comparing the readings of a digital pressure gauge with the readings recorded by TPMS.

Individually record the pressure of each tire with the help of a digital pressure gauge. Then, see the reading on the car’s display panel recorded by TPMS. Whichever tire’s reading deviates from the actual readings, that tire has a bad sensor.

Method #3: Filling and deflating Tires

The third method involves filling and deflating tires. This method is a difficult and tedious task.

First, fill the tires with the recommended air pressure. Then, gently release the air pressure of each tire one by one. Note the variation in the value on the dashboard.

If you notice that any of the tires is not sending a signal to display, that tire may have a faulty sensor.

You have known the ways by which you can trace the faulty tire sensor. So, you might be interested in knowing the causes behind the failure of the sensor.

Causes of Bad Tire Pressure Sensor

The tire sensor usually turns bad when its batteries fail, when you replace the tire, or due to corrosion.

Tire Replacement

The tire sensor most likely fails after a tire replacement. There is always a risk of injuring the TPMS sensor while changing a tire, particularly when breaking the bead and removing the old tire with a pry bar.

Failing batteries

Tire sensors are powered by batteries, so when batteries fail, they fail. However, batteries turn bad over the years. They usually have a lifespan of 5 to 7 years. Secondly, the more the car is used, the more batteries get drained.


Heat is another factor that causes the batteries to drain faster. Batteries drain faster in warmer climatic conditions. Similarly, the batteries get heated when you drive the car constantly in heavy traffic, and sensors get used a lot.

How to Prevent Tire Sensors from Damage?

Tire Pressure Sensor is likely to get damaged during tire replacement. However, if you keep a few of these things in mind when changing tires, you can avoid the risk of sensor damage.

Cost of Tire Sensor Replacement

The average cost for replacing a tire sensor ranges from $40 to $100. This includes an average sensor cost of $30 to $70 and a labor cost of $10-30. If you plan to change to all four sensors, that would cost you around $160-400.

TPMS has greatly reduced the tire blowout incidents. So, ignoring a warning from TPMS is extremely dangerous. After finding out that one of the sensors has failed, you need to act immediately and trace the flaw.


We hope that this guide would have helped you know about the TPMS and how it functions. By now you would have been able to trace which tire sensor is bad.