Don't quite understand the tire pressure monitor
 

I just used my new cool tire gauge (Accu-gage EZ Air) to get my pressure to 33psi for all 4 tires. They were all wildly different - between 20 and 29 psi :eek2::eek2: - after having filled them a week before and thinking all was more or less fine. I had a feeling my pencil gauge was useless and there's the proof.
Anyway, after filling the tires, I just drove off - didn't press the button near the brake - and after a few miles the tire pressure monitor light came on. :confused: Is this because I didn't press the button and the car wasn't expecting the tires to all be the same pressure (since they probably haven't been for a year and a half, the last time my car had a service) or might there be something else wrong? The light was not on previous to the pressure adjustment. Oh, and I checked the tires after a couple of hours cold and 3 are showing around 31.5 psi and the 4th 30 psi. Could that be enough of a difference to trip the warning light?
thanks for any enlightenment.

Any time you make an adjustment to your tire pressure it is advisable to reset the tire pressure monitor. If you don't reset you are likely to get a light in your future because the system constantly looks for a difference in speed between each individual wheel. If any one wheel differs from previous memory the light will illuminate. Don't ask me to tell you by how much it has to differ, because only MINI knows :lol: .

yes - if you had that much change while filling them it is not unusual to need to reset the system....

if you know the pressure is good just reset the light . . .

remember the GEN1 system determines there is a tire pressure problem by comparing the rotation speed of the wheels (variable due to change in circumference due to the fill pressure). SO, the tire needs to spin for a while b4 the system can detect a change

that's what I had thought, but in that case, I would have expected to see the light before fixing the pressure, not after, since the differential pressure was so much greater before. In any case, I'll just reset the light next time I take the car out and hope the light goes out after a few miles. thanks for the help.

It depends on what the exact tire pressures where, and which tire(s) were low. Your TPMS only compares the two tires that are on the same axle, so if (for example), the rears were 20 and 23, and the fronts were 27 and 29, then the TPMS system might not have detected a problem.

So I pressed the button this morning and the light went off after a couple of miles! :thumbsup: I love it when solutions are simple.
Now I just need to take care of the airbag light.....

And throw away that pencil gauge! :grin: