Last night the TPMS System Failure message shows up on the screen on the way home. I have 23 series tires in the rear so I panicked a little, and my girlfriend drove the car earlier in the day. I immediately thought I had a flat and accusingly asked her what she ran over on her way to the gym. Pulled into nearest parking lot and all for tires were just fine. Came home and started doing research and it was all the usual info, bad sensor or low battery etc. I did see a couple post blaming a USB phone charger for the issue. Last week I was out of town and purchased a cheap double USB charger at the mall. It was still plugged into the rear seat lighter. I unplugged the charger and on the very next start the warning was gone. Seems odd that it can interfere with the system but it did and I'm glad I didn't have to pay dealer to solve issue. If anyone else has this warning pop up try unplugging phone charger first. Easiest fix I've had so far!

 

I wonder if it was putting out RF interference and preventing the sensors transmitting cleanly?

It may be unfair to equate cheap with poor quality (noisy RF) but if you spend any time watching bigclivedotcom's YouTube channel you come to expect it.

It might have been a coincidence though if it was only during that one trip as it sounds like the USB charger was unplugged before the next ignition cycle? On my F-Type when more than one tyre is low pressure it reports it as a general fault rather than raise warnings for each one, and although I have not had low pressure on my X351 so far it might have been that. It may be worth checking the tyre pressures to see if a couple are borderline as a small change in temperature can be a couple of psi difference. The pressures should be checked every couple of months anyway, although I have never met a driver who does.

 

I pulled over immediately and everything appeared fine. Then I went to air pump to check if a slight decrease had occurred that I couldn't detect visually and all 4 tires were exactly the same. I turned the car off and on hoping that was going to reset it. Then I let it sit overnight hoping that time would help. So all in all it probably went thru 8 engine starts. It was a few mins late to go by the local mechanic to plug it in and see which sensor had failed. So then I started researching online and it seems like the logic is that the antenna that receives the signal is in the center of the car under the armrest storage. Because of its location and the location of the cigarette lighters there is interference with certain USB chargers. Apparently it is a common problem with Ford owners.

 

Ah ha, I didn't realise you had stopped/started so many times. That does tend to rule out an intermittent fault.

The TPMS system has 4 initiators attached to each wheel arch liner which receive the corresponding signal from each wheel sensor. It is then a hard wired connection to the car. That's not to say RF noise wasn't interfering with the wired side (the cables are not shielded) but more likely the USB charger was interfering with the wireless signal. That would coincide with a couple of the reports I found online where people reproduced it through testing.

USB chargers are one of those things where it pays to buy a reputable model - not just car ones but particularly mains ones. There are so many shocking examples out there... pun intended!

In case you're interested, that antenna in the centre console is for the keyless start feature which detects your keyfob. If that can't pick up the signal for any reason you get a "keyfob not found" message on the instrument cluster and have to hold the key next to the transmitter by your knee so it can read the transponder the old fashioned way.

 

The TPMS system failure message is different than the low pressure warning you get with low tires.