[bmw_python]

i'm getting the warning message? Does the 2006 BMW 325 even have tire pressure sensors in the tires? I checked with AI and it said this wasn't even done before 2007. I got they use an FTM system that measures pressure by speed rotation. I stopped by a mechanic who plugged his computer in to my car and it showed nothing. He did see the the tire pressure was a little high so he adjusted the tire pressure What should I do next? Any suggestions?

[oVeRdOsE.]

FTM system is the best imo.

no maintenance, no connection issue, no issue when changing tire sets.

However, less precision and wont tell you which tire is low.

But hey, car guys look at their tire pressure every weekend , right?


So yeah :

- make sure all your tire are the same size.
- same pressure
- reset the warning

and see if it comes back.

I believe the FTM monitor speed difference from the right or left side, not front/rear. Because I was running a larger outside diameter tire set in the rear and never got the warning, but when I had 1 tire leak.

[Tambohamilton]

Originally Posted by oVeRdOsE.

I believe the FTM monitor speed difference from the right or left side, not front/rear. Because I was running a larger outside diameter tire set in the rear and never got the warning, but when I had 1 tire leak.

When you reset, it calibrates when you next drive the car. So it doesn't really matter how your tyres differ from stock, or eachother, because any discrepancies are accommodated by the calibration. That does mean that your tyres really should be properly inflated etc when you reset, though.

[lowrydr310]

Originally Posted by bmw_python

He did see the the tire pressure was a little high so he adjusted the tire pressure What should I do next? Any suggestions?

As others already stated, your car uses FTM which determines if a tire is low based on wheel speed. Check the owners manual if you have one, it explains how it works. You're supposed to set the tire pressure in each tire then reset the FTM aystem - the computer will determine the current pressure as the baseline, so of one tire loses air it'll have a smaller diameter and spin faster, triggering the warning. If you add air and don't reset the system it won't work properly, reset it after setting the pressure in all four tires.

[oVeRdOsE.]

Originally Posted by Tambohamilton

When you reset, it calibrates when you next drive the car. So it doesn't really matter how your tyres differ from stock, or eachother, because any discrepancies are accommodated by the calibration. That does mean that your tyres really should be properly inflated etc when you reset, though.

no, because if you reset it without putting air in it only to get rid of the warning, it will come back in few km.

reset is simply to remove the warning. The wheel speed sensor will still see a speed gap from left to right, and will still throwing a code.

the transfer case will accept a 3-4% tire size difference from front to rear, which I had. And I never had any code, nor any issue in 55k km that the set lasted. But a 6-7psi difference from left to right = immediate code, and doupt a 6-7psi gap is a 4% diameter difference...

[Tambohamilton]

Originally Posted by oVeRdOsE.

no, because if you reset it without putting air in it only to get rid of the warning, it will come back in few km.

reset is simply to remove the warning. The wheel speed sensor will still see a speed gap from left to right, and will still throwing a code.

the transfer case will accept a 3-4% tire size difference from front to rear, which I had. And I never had any code, nor any issue in 55k km that the set lasted. But a 6-7psi difference from left to right = immediate code, and doupt a 6-7psi gap is a 4% diameter difference...

https://ia600902.us.archive.org/26/items/BMWTechnicalTrainingDocuments/ST056%20Chassis%20Dynamics/08_Tire%20Pressure%20Monitoring%20Systems.pdf
Page 14. Maybe yours is different, but mine will accept the new "zero" if I reset FTM without altering the tyre pressures that triggered it.