Tyre Pressure Monitor gremlins...?

[soapywalrus]

Hit a piece of metal on the M1 on Friday. It holed the sidewall of the left rear tyre and put a little ding in the rim. The TPM activated exactly as it's supposed to, for which I was very grateful! I stopped, put the spare on, and continued.Took the wheel to a tyre shop on Saturday morning, they replaced the tyre, checked the rim, pressure tested it and were happy that it was still sound. They rebalanced the wheel and I took it home and re-fitted it. Test drove it, then held the TPM button to reset it with the new wheel on.Drove the car the rest of Saturday, Sunday and Monday. On the way to work this morning the TPM went off again. I was close to work so nursed it in and checked all the tyres thoroughly. No air leaks, nothing sticking out, all appear inflated perfectly.Left the car at the back of work all day. No flat tyres. No air hissing, nothing.So, what could it be?can the heat affect the TPM? Could it be because the tyre fitters have put slightly more air in the new tyre than I have in all the others? If that's the case, why would it take three days for it to register?Anybody had similar problems?

[psycholist]

Fundamentally the TPM just uses the ABS sensors to check whether all the wheels are the same circumference rather than directly monitoring type pressure. If the replaced tyre is at a higher pressure as the tyres warm on a long drive it may manifest as a change in the wheel circumference big enough to register. Reseating the tyre may have changed things, but that doesn't explain why the warning has showed up after you reset the system. I'd keep an eye on the tyre pressures for a few days and see if there's a slow leak.

[soapywalrus]

Thanks.

Think I will take it to the garage tonight and reset all the pressures so I know them to be the same. Then I'll reset the TPM and see whether it goes off again. If it does, I'll check the pressures again and if they've not changed then I guess it's a problem with the monitor.

Just a though - the new wheel is new (obviously)

All the other three are about 18,000 miles old. Could it be that the additional tread on the new wheel is enough to trick the TPM into thinking that the other three wheels are slightly down?

[psycholist]

Since you set the TPM after fitting the new wheel it should already account for the slightly different wheel circumference from the new tyre. Having the warning light back means something has changed since you last reset it I presume.

[Wardy]

I see there's some VCDS sections and coding for TPM. Such as:

Audi TT (8J) Tire Pressure Monitoring II - Ross-Tech Wiki

I wonder if there's any fault logged? I would have thought a system reset on the TPM would have done the trick though.

The fact you have a brand new tyre with maximum tread on one side of the axle will affect the system, but again, resetting should tell the system that in this state everything is OK.

Go through the motions as you say above, I think that makes sense. And if you've not got access to VAG-COM and want a scan, let me know.

Steve

[gadgetman]

Always reset it cold if poss, before driving on the new pressure.

The threashold is 3PSI, which a hot tyre can be over the set pressure by 3-4PSI. That's why when I'm out and about in the works car, and check them, I set them 3 PSI higher than the label on the door pillar.

[sms]

I'm having the same since a blow out Friday, they replaced the back tyre and now after they have warmed up the tpm goes off. Each tyre has the exact pressure, wondering if the tyre rating or make makes a difference?

[Tech1e]

Only tyre size would make a difference.

[Dallan]

i had this with one of mine recently was dropping a small bit of pressure every 3-4 days and the TPMS would ding, turned out to be a small leak at the valve stem, tyre fitters replaced it and ok since

[sms]

My car is a w rated tyre car, front are y and one of the back is y and the other w could this be the problem the w rated one is the newest and the other back one (the y rated one) is half worn ?

[Dallan]

My car is a w rated tyre car, front are y and one of the back is y and the other w could this be the problem the w rated one is the newest and the other back one (the y rated one) is half worn ?

No the W and Y are just the speed rating, doesn't affect the size of the tyre

[sms]

Well problem solved the tyre was flat yesterday morning but the garage couldn't find anything wrong, as the tread was getting low I decided to replace it, at least I know it works properly.