TPMS light on

Hi,

Each wheel has its own sensor in it which is a part of the valve stem where you place the air. These sensors send a radio signal that is received by the TPMS control unit which is mounted above the throttle pedal.

Since the light is staying on, the first thing I recommend is having the sensors checked. The battery life in each sensor is approximately 5 years. If one fails, the TPMS loses signal, and the light turns on.

To test these, I use a tool designed to indicate a signal from the wheel being tested. It doesn't require taking things apart to check, so I would think a tire shop would be the best place to contact to see if they would take a few minutes and check if there is a signal from each wheel.

You could also have the vehicles can-bus scanned to determine if that is the issue. CAN stands for controller area network. Basically, all computers/modules are tied together via a few wires. This would indicate if there were diagnostic trouble codes stored in the TPMS control unit.

I attached a picture below showing the two components. This is really a lot easier than I likely made it sound. I check them as a courtesy if a customer asks.

Let me know if this helps. Also, please feel free to let me know if you have other questions or if I can help in any way.

Take care,

Joe

See pic below.

Okay, the weather was a bit warmer today and now the TPMS light is off. Could the cold have affected the batteries in the sensors?

Hi,

If it came on when it got cold and off when it warmed up, that is a very common issue and nothing to worry about.

The air in the tires contracts when it gets cold. As a result, the pressure drops. If it is low enough, it will turn the light on. Once it starts to warm up and the air begins to expand, the pressure increases, and the light goes out.

This time of year, it is not uncommon for me to have 3 or 4 people stop in and ask why their light is on.

I have a feeling that is what happened. It could be a weak battery, but let's see if it happens again. If you open the driver's side door, there will be a label that has the recommended tire pressures. If the light is on, check and confirm all tires are at least to the manufacturer's specifications.

Let me know how things work out for you.

Take care,

Joe

When the light came on, I checked, and all 4 tires were at like 25PSI. I filled them up to 33PSI like the label says and the light continued to stay on until today when the weather got warm.

Hi,

Run them at 35 PSI. Remember, once you increase the pressure, if it was cold enough, it would still drop. If you put them right at 33, it wouldn't be odd for them to drop to 29 or 30.

If this does happen again, let me know. It could be a weak battery. However, the only way I know to test it is if you have a tool that can read the signal from each wheel.

Give it a couple of days or until the temp really drops to see if it comes back on. If it does again, reconfirm pressure. If it is at least 32 psi, then we need to check the sensors themselves.

Take care,

Joe

Okay, the TPMS light came on again then back off after a few minutess. It's not even cold today, maybe 50F. I don't think it's tire pressure since This isn't the tire pressure light that looks like a flattened U with a ! this light just says TPMS. I suspect it's one of the wheel sensors but the problem is catching it when its actually on to see...

Hi,

I'm not sure which way would be best for you. However, I have a tool that is specifically designed for the TPMS systems. I can scan at each wheel to identify pressure, tire temperature, radiofrequency, and battery life. It takes me no more than 5 minutes to do it. If a shop doesn't have a tool like that, then the next best thing is to scan the can-bus.

CAN stands for controller area network. Basically, all the different modules/computers are tied together via a few wires. This type of scan would likely be a bit more expensive. Here is a link that shows how it's done:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Even if the light is off, a code should still be stored indicating an intermittent issue.

Let me know if I can help you in any way.

Take care of yourself,

Joe

Is the CAN bus the same as the diagnostic port? My neighbor has a code scanner.

Hi,

The can-bus is read through the port you mentioned. If your neighbor has a scan tool that can communicate through the CAN, yes. Many of the less expensive scan tools cannot read them. They are specifically designed for engine codes also known as (P codes) and are unable to retrieve codes from other modules.

Joe

Just an update: since the weather has warmed up, I've not seen the TPMS light come on anymore. I guess those few frigid nights we had messed with the batteries in the wheel sensors.

Hi,

Thanks for the update. Most likely, it was a battery, or the air pressure was affected by the air temperature. Regardless, I'm glad it's not giving you any more trouble.

Please let me know if things change or if I can help in any way.

Take care,

Joe

Okay, the light has been off all year since then, until it got down to like 6F one night and it has been on since then, even after the weather has warmed up. I guess I'll go to a tire shop to have them wave their wand and see which wheel it is.

Hi,

Have you checked the pressure in each tire? You may find one that is low enough to turn the light on.

Let me know.

Joe

All four tires are 33-35PSI. And guess what? The TPMS light has been off for the past few days. I really think it's one (or more) of the batteries in the wheel sensors just can't stand the cold and throws the light on.

Hi,

That is very possible. The batteries are expected to last about five years, so it's possible.

I don't know where you are, but if there is someone that has the correct tool, they can tell you if there is a weak battery. The one I use is for reprogramming a new sensor, and it can tell me the tire pressure and air temperature in the tire. Also, and more importantly, it tells me the condition of the battery.

The tool is held near the valve stem, and nothing is actually connected. It simply reads the radio signal from the sensor.

Let me know if you have anyone that can do that for you.

Take care,

Joe