clochner

Last night my tire pressure monitoring system light came on. Says there's some kind of error. Strange, because I haven't even used it once since getting the car in August. Has this happened to anyone else?

NWS4Guy

Not an error, but I got the warning last week with the cooler weather we have been having, that I needed to check all tires. They were a little low (33 or so) so I brought them back to 41PSI and reset the TMPS in the MMI so it could recalibrate with the changed pressure. All has been well since.

clochner

Okay - makes sense. The temp has been dropping here in Chicago the last few days. So I'm supposed to reset the TPMS once I fill up the tires, right? Also, is 41 psi the recommended amount?

Tifosi

Tire pressure should be checked about once per month, especially when seasons change. If you are keeping the pressure constant from one season to another, there is no need to reset the system at all.

NWS4Guy

Anytime you change pressure you need to reset the TMPS so it can recalibrate. You can check the recommended pressure in the door jam for your car.

Tifosi

Let's say if you have the system set at 41psi all around, and you are only refilling it back up to 41psi, do you still have to reset it ? You only need to reset it if you are changing the setting, say 38psi, correct ?

IAS5

resetting the TPMS basically means you are resetting your new baseline for it to measure against.

If you want to intentionally set your tires to 36, for example, inflate/deflate to 36, then reset TPMS via the MMI. New baseline is now 36.

NWS4Guy

If you are holding the same, you don't have to, it works like Steve says above. I prefer to reset it after touching the PSI in any tire, because it's not actually measuring pressure, it's measuring the change in rotating diameter of the tire using the ABS system. Can I tell if I have 41.0 or 41.9 using most tire guages? Not really, you usually have 41-ish pressure in there, since you really have no clue how accurate the guage is, and that is also assuming you are using the SAME guage each time (not everyone does).

If I reset the system, it will start at a new baseline and tell me when I have deviated the % diameter rotation based on the MMI calculations it uses and I know it's using the latest pressure data, rather than assuming I have it back to where the measurements were set from the last time.

b_desmo

add about 1 psi for every 10 degrees drop in temp = if you fill up you tires in a warm garage (say 65) and normally drive when its 20-30 +/- need to add 4 PSI

Its all a bit of a guessing game but I personally haven't had the MMI notice and I think I ran 44 last year (calibrate MMI @ 41)