Mysterious TPMS Problem

[Diesel Tom]

I've got an unusual TPMS problem. My son drives about 60 miles one-way to work each day. About half way through each leg of his trip, he gets a TPMS system failure message (not an individual tire pressure warning). Most of the time it will go away on its own in a few miles. I have replaced the sensors twice, first with Motorcraft and most recently with Standard sensors. I had bought the Motorcraft sensors from Amazon and it appears that they were old stock (approaching 10 years old).

Could it be a problem in the SJB which houses the receiver for the TPMS system? Is there an antenna that could be damaged going to the SJB?

 

[Rcflyer330]

The best way to start is by using a scan tool that can read all the systems and see what codes come up for the tpms system.

If you dont have an scan tool that can do that it might be a good idea to get one. I would recommend a elm based obd2 adapter (cheapist option) or an obdlink adapter (more expencive) and forscan / forscan lite (lite is the phone app).

I dont know for sure but your local autoparts store may be able to the codes.

 

[DavidEBSmith]

For quite a while, we would often get a TPMS system failure after driving for about an hour, which would always go away. There was never a code that pointed to a particular sensor. It stopped when we unplugged the Bluetooth-to-audio-in gizmo that we were using for hands-free phone. I'd have to conclude that it was causing some interference that triggered something that the TPMS system took an hour to get upset about.

 

[Diesel Tom]

David, it certainly looks like we are experiencing the same problem. Drive the car around town and the TPMS indicator never comes on. Drive it on the road and it comes on after you have been on the road for a while. The TPMS indicator goes off on its own. I'm going to try a run without the factory satellite radio turned on. We do not use any Bluetooth devices while in the car.

I'm an electrical engineer by training and vocation. I wondered if there was an interfering signal at the frequency of the TPMS sensors, 315 MHz. In checking the government frequency allocation chart, I see that 315 MHZ is in a government exclusive frequency band, not a public band. I guess it's not impossible that there is an interfering signal out there, especially along an Interstate Highway.

Does anyone know what frequencies are used by the automated toll equipment along our Interstate Highways? Just wondering as we have had a bunch of new sensors installed along this stretch of highway. (BTW, we do not use the automated toll system)


(edit) Just found out that the automated toll systems operate in the 900 MHz ISM band, so no interference here.