TPMS hysteresis

[rmicroys]

I just had my TPMS system trip off on me. The last time I adjusted my pressures in September, I was at the track, and bled my tires down to 36 hot so that I didn't destroy my tires. Then I've been driving like that ever since without any TPMS warnings. Until yesterday, the temps here are now in the low single digits Celcius and after being parked outside it all day at work, it tripped off on my way home. So, it ended up just being that the cool weather just lowered the pressures enough to set the warnings off.

My good pressure gauge was still in my track kit, so I had nothing. Stopped by the local store, bought one of those cheap pressure gauge "stick" types, and checked all my tires, they were in the range of 34 psi. All of them. So I go home, pump them back up with another gauge on my compressor line, and still had issues (even though the filler gauge on my compressor read 39, evidently it wasn't) Drove around today and eventually picked up another Longacre gauge, digital, accurate to 0.1 PSI and then filled the tires up to the sticker pressures and finally the **** warning goes out.

What's the sensitivity on this stupid system (and the fact that it doesn't display all four tires on the screen is complete stupidity on Audi's part)? How close back up towards the sticker pressures does one need to get to before the **** light turns back off? How it is reacting seems to me like it has some sort of hysteresis built in. ie, it allows a lot of variation as the pressures drop, but once on, you need to fill them all back perfectly before the warnings turn off. Anybody see this?

[mngolfer]

I had this happen at the track with my Hoosiers. The Trackside tire owner told me to set my cold pressure at 28 PSI. The TPMS was fine the first day. The second day the TPMS came on. Increasing the pressure even one PSI lower than specified would not make the TPMS go off.

[dvmmike]

So does anyone know the exact pressure that will reset the warning light?

[toecutter]

I reset with my VAGCOM on each tire change. As I understand the system, the computer has a minimum setting per these instructions: My stock setting on the new spyder was exactly as indicated in the example.

http://wiki.ross-tech.com/wiki/index...itoring_System

[KfabR8]

Wow - I never realized that the Ross-Tech site had that sort of info on it. Actually never thought to look. Thanks for sharing that info.

I was having issues when I put the winter tires on the car with the TPMS sensors not being picked up. I went through the coding and instead of changing anything, I just said "do it" and it took the sensors w/o any more issues.

Ross-Tech <--- Good stuff!