TPMS Low Pressure warning light triggered, but tires are good on pressure

[BRGT350]

The other morning my TPMS Low Tire Pressure light triggered with the warning on MFT. I checked tire pressure when I got to work with a cheap tire gauge I keep in my glove box. Everything looked to be in spec, 37psi front and 35psi rear, which is where I set the sensors using the trigger tool this spring. I checked the tires at lunch after they had cooled from the morning commute and again before I left work, all were good. Drove home with the light on and checked with my high quality gauge and they were still good. The light has stayed on since Monday morning.

I have had a sensor go bad before and that gives a fault message after 20 minutes of driving and tends to go off after restart. It would also go off when I would get home and the car picked up the sensors in the winter tires. The message on Monday was low pressure and not for a fault. I also have the Cobb AccessPort installed and my VHR doesn't work anymore. Should I uninstall the AP, see if the VHR runs to indicate which tire is at fault or if the light resets? When I have had the light illuminate on my 2011 Fiesta or the 2013 Escape, it was from a tire being low and usually from cooler temps. Adding a little air in the fall or winter made the light go back off. The ST doesn't have low pressure and the temps are above average.

I searched and found a similar reported issue, but no resolution was reported.

 

[CanadianGuy]

A few thing of things no order. 1 The FiST does not remember more than 4 TPMS sensors so it will not pick up the Winters. I hate that but I tested that at length as my Edge could.

I know a couple had TPMS issues and the failure was the transmitter. Using the reset tool one tire would never send the signal. that one sensor has to be replaced.

One last hail mary solution I have seen work if the sensor transmit is to release the tire air, get the sensor to transmit the signal of low then reinflate it. Problem with that is knowing which wheel and running on the spare while the other is in the boot.

So unfortunately no easy fix but if you have the reset tool it will be a quick diagnostic.

Good luck

 

[BRGT350]

thanks for the info. Oddly, both our Escape and Fiesta remember the summer and winter sets of tires. My 2011 Fiesta would not remember them. This spring I replaced a bad sensor in one of my summer wheels and had to retrigger all 4 of them. Took a couple of attempts to get the new one to register, but learned that it helps to move the car so the tires complete a few rotations to wake up the sensor. That worked great. When I had the bad sensor, it would give me the "TPMS Fault" warning on the MFT screen. I could try and dump air pressure on all 4, retrigger the sensors, and refill with air and see if that helps. Do you know if the VHR gives you information on what tire is low? That could help narrow down the issue.

 

[CanadianGuy]

Damn mine would not learn both and all the people I spoke to in Canada have the issue when switching the winters out. So much so a few of us have the reset tool and do coffee meets to address them. I do not know if the VHR does as I never had an issue but it should as the car registers by corner.

 

[BRGT350]

I will do an uninstall of the AP and run the VHR and see what comes up.

We have one trigger that my dad, brother, and I share. Typically I leave it at my house and they just stop over in the spring and fall to reset the sensors. We all live close by, so it is easy for us.

*UPDATE: I uninstalled the AP during lunch, but the car still won't run the VHR. That won't help narrow down or even check if the VHR gives a specific tire to check out. On a separate note, driving with the AP uninstalled feels like I am towing an anchor behind the car. Forgot what the car was like without it.

 

[JasonHaven]

Mine popped up yesterday, about to uninstall my AP this morning, then set an appointment with the dealer. Definitely not low on air, though I don't know what my specific pressure is.

Re: VHR, you can't have anything plugged into it the OBD port when you run. I use an 'Automatic' OBD scanner to track mileage, and it won't run the VHR with that plugged in.

 

[Racer83L]

it sounds silly, but did you check the spare? I dont know about the fiesta but I own 4 Transit Connects and 2 were having this issue, checked the spare, it was low on air. filled it up all good to go. If you think about it it makes sense for the spare to trigger the light because what good is a flat spare?

 

[CanadianGuy]

it sounds silly, but did you check the spare? I dont know about the fiesta but I own 4 Transit Connects and 2 were having this issue, checked the spare, it was low on air. filled it up all good to go. If you think about it it makes sense for the spare to trigger the light because what good is a flat spare?

Good idea but the user manual states the spare does not have any TPMS nor does the reset monitor function call to reset it.

 

[BRGT350]

correct, there isn't a TPMS monitor in the spare.

I did have one tire that was 1.5psi lower than the others, so I added some air and drove around to see if the light would go off. It did not. I did eventually get the VHR to run and it was useless in helping out. I reprogrammed all 4 TPMS sensors and the light is now off.

 

[CanadianGuy]

correct, there isn't a TPMS monitor in the spare.

I did have one tire that was 1.5psi lower than the others, so I added some air and drove around to see if the light would go off. It did not. I did eventually get the VHR to run and it was useless in helping out. I reprogrammed all 4 TPMS sensors and the light is now off.

Strange maybe there was one sensor/tire that had a high pressure when you first relearnt it and now that the pressure is normal it was considering it as low. Else maybe a battery getting into a low state but usually they are good for at least 5 years.

 

[BRGT350]

When I had a battery go out in one of my sensors, it gave me the "TPMS Fault" message. I reprogrammed the sensors and had one that would not work, so I swapped it out and it worked. I would not rule out battery issues since the sensors in my summer wheels/tires are actually out of my 2011 Fiesta. They are now 5 years old, or at least 3 of them are. When I had the dead battery in the sensor, the light would go off when I would pull into the garage and the winter tires would be picked up. The next morning after 20 minutes of driving, the light went back on. This went on most of last summer until the winter tires went on. This spring I replaced the sensor.

With my 2011, I ran without TPMS in my summer tires, but I sold my stock 2011 wheels and tires to my brother with the sensors still installed. The deal was that when he replaced the tires, he would give me back the sensors. If we drove down the highway together, I could get close enough to him that the TPMS light would go off on my 2011. If I dropped back, the light would come on after 20 minutes. Kind of fun to play with on the highway on a long trip.

 

[jeff]

And another question, has anyone used one of these devices?

http://www.ebay.com/itm/Ford-Tire-P...ash=item2c9c27f19f:g:3aYAAOSwl8NVdynf&vxp=mtr

Seems worth $40 if this continues to be an issue, I'd rather spend $40 and have a lifetime fix as opposed to visiting the dealer every so often for a reset.

 

[BRGT350]

My TPMS sensor light comes on every few weeks after resetting it. I just leave it on since I will be on winter tires in a few weeks. I think the batteries in the sensors are starting to go out. You can get a trigger from TireRack and reset them without a dealer trip. It isn't uncommon that after a pothole strike that a few pounds of pressure leaked out from the bead. It doesn't take too much of a pressure drop to trip the light. I get the light in the winter if I program the sensors on a 50' degree day in the fall and the temp drops to single digits months later. I have also had a tire on my Focus lose about 5psi or so on a pothole strike. Add a few pounds to the tire that hit the pothole and see if the light goes off.

So far, my ST has never been to the dealer.

 

[jeff]

Thanks Brian I think it is.

Yes I checked all the levels, they are fine, but the light remains on.

Glad to hear you've been dealer-free thus far.

Tell me more about this TireRack thing....

 

[CanadianGuy]

Thanks Brian I think it is.

Yes I checked all the levels, they are fine, but the light remains on.

Glad to hear you've been dealer-free thus far.

Tell me more about this TireRack thing....

Tool to reset: http://www.ebay.ca/itm/NEW-TPMS-TRA...PMS-19-TPMS19-FORD-8C2Z-1A203-A-/151655334128

I have one in the glove box and share with the locals. ANY tire shop worth anything has one as well.

 

[vegas_]

Well I've had my FiST for 12 months now. Stock tires. I checked the tires when I go the car and they were at 43PSI all around
I guess the dealer (or factory ) set them to that, even though the tag says 39/36. But I forgot about checking them again.
I had noticed a drop in MPG a few months back, that I attributed to hot weather and heavy A/C use.
But last week the TPMS warning light went off, I though maybe I had a flat, I pulled over and quickly checked all 4 tires, they are all at 32PSI
Thinking that was OK I proceeded and decided I'd figure out how to reset the warning light when I got home.
Only then did I realize that they we way under pressure, the sticker says 39F,36R.
SO I filled them all to 44 (the tires say max PSI is 50) The warning light went off by itself.
And now after a week the computer is indicating much higher MPG, but the weather is colder and not using the A/C much, so I'm not sure how much of that is due to A/C or tire pressure.

11 PSI seems like a lot of air to lose, but all 4 were the same, so it's not a bad tire.
Maybe since the tires are small, a tiny loss of air, reduces the PSI a lot, or maybe temperature changes?
In any case, I need to check the tire pressure more often than once a year.
Or maybe figure out how to recalibrate the TPMS to trigger at 36 or so.

 

[Capri to ST]

Tires can lose about 1 PSI per month just from air molecules escaping the rubber, this is normal and expected, so that's right about where you were. They can also lose or gain 1 PSI from every 10 deg. change in temperature, so fall is a time when they drop a lot.
I recommend getting a good quality gauge and checking them once a month. If you keep up with them, you'll never see the TPMS light unless there's a problem.

 

[M-Sport fan]

^^^I check them once a WEEK (at least), so I can easily live without the TPMS sensors in my 1.2 wheel summer setup.

I just wish that there was a way to 'write out' the WHOLE TPMS system from the car's BCM (IF that's where it is located?) to not even have to see the cluster light at all.

 

[Capri to ST]

The only time mine activated I had picked up a nail and the tire was down to 15 lb. or so. The TPMS light prevented me from driving off with the tire that low, because it didn't look that different. I like having it as a backup.

 

[FiST_Pounder]

Then there's this

http://www.ebay.com/itm/Ford-Fiesta...ash=item2a8205c994:g:zxYAAOSwjvJZUmIt&vxp=mtr