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Tire pressure monitoring systems only became mainstream 20 years ago. Invented by Bosch in the 1990s and only available on luxury brands like Mercedes or BMW, they became a legal requirement for all carmakers in 2012.

Like many car safety systems, we don’t even know they’re there until we get a warning light on the dashboard. Sometimes when the TPMS light flashes on your dash, it’s obvious when you check the tire that the reason was a very underinflated or flat tire.

The low tire pressure indicator may blink or glow even if your tires are in good condition. This might be the result of a slow but sure tire leak. Sometimes, a defective TPMS may also be the reason.

The 4 Reasons The TPMS Light Flashes Even Though Tire Pressure Looks Okay.

Drop in Temperature Overnight.

In severe wintery spells, the temperature can drop way below freezing.

Air pressure drops by up to one psi for each ten Fahrenheit reduction in temperature.

Most TPMS systems are programmed to alert the driver when there’s been a 25% reduction in air pressure in the tires. This can be achieved in very cold temperatures and is the main reason the warning light comes on in winter.

Although cold temperatures are the most likely cause, others to consider if the weather isn’t extreme are:

Tire Rotation

Most people rotate their tires every 5000 miles. It helps even out tire wear and increases their lifespan.

Sometimes, the sensor inside the tire doesn’t pick up the correct tire pressure for a few minutes after rotating. If you have just left the tire shop and your TPMS light is on, give it five minutes of driving to see if the system resets and learns the new tire positions on your car and the light goes off.

If not, pull over and check your tire pressures to ensure the tire shop has inflated them correctly. If the tire pressure looks good, take it back and ask them to check your tires over. Perhaps the sensor wasn’t seated on the valve correctly, or it isn’t wirelessly transmitting the pressure back as it should.

The TPMS Sensor/ Speed Sensor is Damaged

Direct TPMS

The pressure switch is in quite a vulnerable position and faces a lot of abuse along with the tire and rim. It suffers from road vibration, but it’s also subjected to heat, cold, and moisture. All these can cause it to fail.

They should last between five to ten years, depending on the environment the car has been driven in.

Also, using run-flat tires and sealants can cause issues with the pressure switch and cause it to fail prematurely.

Indirect TPMS

These systems rely on ABS speed sensors to distinguish if one tire is rotating at a different speed from the others. There is no pressure sensor inside the tire. These exterior sensors are even more exposed to the cold and wet and do fail.

Older, less luxurious cars usually have this cheaper TPMS system. A permanent ABS light often accompanies a blinking TPMS dash light as they share the same speed sensor.

Spare Tire

Due to the increase in space-saver tires and run-flat tires, many cars no longer have a full-size spare. The ones that do may inadvertently have a TPMS sensor inside them. This shouldn’t happen, as the ECU control module can only read four sensors.

A Spare Tire Shouldn’t Have A TPMS Sensor.

If your spare tire sensor is being read, it means one tire outside the trunk has a sensor that isn’t working or doesn’t have a sensor at all.

When Is It Normal For The TPMS Dash Warning Light To Be On?

The ECU goes through various checks to ensure your car is roadworthy when you first start your car. Sometimes oil and engine check lights can stay on for a few seconds. This also applies to the TPMS check light.

So if it’s only illuminated for five seconds before going off, all is good.

Going off and coming on when you’re driving signifies either an issue with the pressure in your tire or the sensor is not working correctly.

Unlike indirect systems that can’t tell the driver which tire has low pressure, new modern direct TPMS systems with sensors inside each wheel indicate which tire is low on pressure.

TPMS faults generally come in three categories.

  • The first is that the light will flash in your dash and stay on.
  • Secondly, it goes on and off for no apparent reason.
  • And the third one is it stays on all the time.

Let’s look at these individually.

  • Flashes and staying on are signs of something wrong with the TPMS system. The ECU has requested a tire pressure reading but has been unable to do so.
  • It stays on all the time. Again, this is indicative of a more permanent problem. You should take your car to the dealership or the tire shop to be inspected.
  • Finally, it comes on sometimes and then goes off again. This more likely occurs during rapid temperature fluctuations. This is most commonly noticed in the winter when temperatures drop rapidly overnight, and the driver gets in the car and notices a TPMS light is on. The good news is that as they drive, the tire pressure increases due to the friction on the tires, increasing the air temperature inside the tire and raising the pressure. Quite often, the light will go off after a few miles.

Although it’s important to check tire pressure regularly, it shouldn’t be done in extremely cold conditions. If you were to fill your car tire with air when it’s extremely cold, as soon as the temperature rises, the pressure in your tire will increase and may well go above the maximum recommended psi.

Can You Drive with a Flashing TPMS Warning Light?

It’s best not to drive if you see the light on the dashboard.

However, if you are confident that the tire pressure is adequate, your tires are in good condition with no sign of wear, and the valve is holding air properly, you might feel that you can drive it to a shop to get checked over.

How Much Does it Cost to Fix a Blinking TPMS?

Depending on whether you have a direct or indirect TPMS system will affect the cost of replacement

or repair

Direct TPMS

Direct TPMS is the best and most modern system, as it tracks specific pressures on each tire. The signals are sent via wireless transmissions to the car’s ECU and dashboard panel. The ECU is programmed with an upper and lower pressure threshold limit, and should either of these be exceeded, a warning, either audible or visual, is heard or seen in the dash.

Direct TPMS Pressure Sensor on Rim

Although more parts can fail, a direct TPMS will indicate which wheel is causing the problem. Each sensor has a battery that sends a wireless signal to the ECU. Like all batteries, they don’t last forever, and when they are fully drained, a TPMS warning light will come on in the dash. A TPMS battery should last seven years and are an easy replacement for a tire shop to make. The battery sits inside the sensor housing attached to the valve inside the tire.

If the battery’s good, water may have damaged the sensor, so look for a damaged valve stem or, if you are inside the tire, a perished rubber seal.

Indirect TPMS

Indirect TPMS is the cheapest system that utilizes the vehicle’s ABS. It recognizes an underinflated tire as its diameter increases, which causes it to spin less slowly than the properly inflated tires. However, it won’t tell you which tire is at fault as the direct system does.

ABS Speed Sensor Cable

Driving styles and uneven road surfaces can play havoc with indirect TPMS and the speed sensor’s readings sent to the dashboard.

Servicing TPMS System

There is no need for set maintenance on the system. However, most decent car shops will inspect briefly as they replace a tire on a rim.

One of the most important factors is to keep the valve stem in good condition. Because if this corrodes and rusts or the valve gets jammed, it can cause issues further down in the tire itself, affecting the sensor.

Can TPMS Systems Give a Wrong Reading?

Generally, they give correct readings.

Although we may think the sensor is giving an incorrect reading in extreme cold, they are accurately reading the pressure. Bear in mind the switch is operated by pressure. If the pressure drops due to lower temperatures, it won’t allow this.

Cost to Fix a Faulty TPMS system

If your car is under warranty, take it back to the car dealership to get it fixed. If, however, your car is out of warranty, this should not be too much of an expensive fix.

Labor costs are reasonable as the tire, and ABS speed sensors are easy to get to.

A new speed sensor part on an indirect TPMS ranges from $100 to $175, with an additional $100 or so for labor.

A new tire pressure sensor for a direct system is cheaper and costs $50 to $100, and another $100 for labor.

Reset The TPMS System

All car manufacturers have different ways of resetting their TPMS. They do generally follow the same pattern, though. It is always best to refer to the car manufacturer’s handbook for exact details.

Method

There should be a TPMS reset button located in the cabin’s glove compartment or underneath the steering wheel column.

When pressed, the button generally beeps or flashes briefly three times to indicate a resetting is in progress.

The car manufacturer will determine what you need to do next. Some cars require you to drive at a constant speed of 50 mph on the highway for 10 minutes. This will keep the car air pressure in the tires constant and allow the sensor to correct itself.

Some car manufacturers state you should complete the reset by running the car idle for 20 minutes instead.

This method is more common in indirect TPMS systems.

https://youtu.be/VrpC4tZ8bZI

TPMS Reprogramming Tool Method

Most direct TPMS systems reset using a TPMS reprogramming tool plugged into the car’s ECU by an OBD connection. They vary in price and features, but the principle is the same. The tool communicates with the pressure sensors and identifies the ID of any newly fitted sensor and which tire they are fitted to.

Some cars may still require another step to finish the setup, but it doesn’t usually require the car to be driven.

Does TPMS Detect Tire Overinflation?

Indirect TPMS – which measures wheel speed, will not always detect an overinflated tire as the wheel speed may not be altered enough compared to the other tires to register.

Direct TPMS – where each wheel has its own sensor to detect overinflation.

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