Hey all,

My dad has recently purchased an '03 M3. Well, within the first 500 miles the rear tire was punctured through a treadblock and was toast. So we had the tire replaced by the $tealer.

Last night we were out for a drive and the tire pressure light came on red. Ah crap we thought. Pulled over and checked the tire pressures. No problems... They're all within spec with no differences between sides.

Any thoughts or experience here?

I believe you must "train" the tire monitor system. To do this the tires must be cold and to the proper inflation levels.

First you have to reset it correctly.
Then it can light on without any reason.
You'll notice many false alarm from tire pressure monitor.
I find it very useless.

From the manual... page 83.

<b>Initializing the system</b>

Initializing is necessary to familiarize the system with the correct inflation pressures.
Repeat this process after any changes in tire inflation pressure, tire rotation or
replacement.

1. Check the tire inflation pressures in all the tires, comparing them with the
inflation pressure table on page 25, and adjust them if necessary

2. Turn the ignition key to position 2

3. Press button as long as you need to until the indicator lamp in the instrument
cluster lights up. After a little while, the indicator lamp will go out
by itself

4. After a few minutes, the Flat Tire Monitor will accept the current inflation
pressures as the values to be measured against, and from that
point on can detect and report a flat tire.

<b>To activate/deactivate the system</b>

The system is automatically activated in ignition key position 2 and consequently
is on whenever the vehicle is operated.

To deactivate the system: tap the button, the indicator lamp will light up yellow.
To activate the system: tap the button again; the indicator lamp goes out.
Deactivate the system when snow chains are mounted, since false warnings
and undetected losses in pressure are possible under these kinds of conditions.

<b>Flat tire</b>

The red warning lamp in the instrument cluster lights up to warn of pressure loss and tire
failure. In addition, an acoustic signal is sounded. To come to an immediate
stop, reduce speed, while avoiding any sudden, jerky braking or steering
maneuvers.

Fix the flat tire using the M Mobility system, refer to page 133.
To reset the warning lamp: the red indicator lamp has to be switched off manually
after putting on a new wheel. At this point, hold the Flat Tire Monitor
button down until the indicator lamp goes out. Reinitialize the system afterward.
The Flat Tire Monitor cannot provide you with advance warning of
sudden and severe tire damage caused by external factors.
Another factor which the Flat Tire Monitor does not recognize is the balanced
and very gradual pressure loss that takes place in all tires over an extended
period of time.

Check tire inflation pressures on a regular basis, correcting them as
necessary, refer to page 25. Under certain circumstances, there
may be false warnings or a delayed detection of losses in pressure when
driving on snow-covered or slippery road surfaces.
Performance-oriented driving, slip at the drive wheels and high levels of lateral
acceleration can also delay the appearance of status reports in the Flat
Tire Monitor's display panel.

<b>System malfunctions</b>

As long as there is still a malfunction, the indicator lamp in the instrument
cluster will stay lit up yellow. Please contact your BMW center for
additional information.

Thanks all

I'll have him read the manual :devillook

Mine came on falsely several times after I first got the car. It would always do it on this same stretch of bumpy street. I assume it was just a little sensitive. In all cases, I followed the steps in the book to reset the system, and it stopped happening after a while. I think that perhaps it "loosened up" a little bit after those first three or four falses and has never gone off since (and no occasion when it should have either).

Pride355: if yours false alarms (alarmed) so much it probably had something wrong with it -- it works via the ABS sensors, so probably one of those was a little off on your car...

i've had the same problem and took it to the dealer, dealer replaced the switch in the dash...and everything is fine now...btw i took it ot the dealer after resetting the tire monitor following the instructions above....

Originally posted by gork

Pride355: if yours false alarms (alarmed) so much it probably had something wrong with it -- it works via the ABS sensors, so probably one of those was a little off on your car...

Gork probably you are right.
I was told by the dealer that it works via radio frequency. They show me the part on ETK, and there is a part on wheels that was related to radio control but can't remember now. So I was told that it can come up by a false radio signal.

Actually since the car is gone, I don't care much.
The interesting thing was I haven't had any signals from the system during the first 2000 km. Then I checked the tire pressures. Rear tires were 48 psi instead of 35 (Yes eventhough I was told that they were checked in the break-in service at 2000 km) When I lower them to 37 psi, and even after resetting the system, I had several false signals in every week.

I complaint about this to dealer, but they couldn't fix it.

Originally posted by pride355
I was told by the dealer that it works via radio frequency. They show me the part on ETK, and there is a part on wheels that was related to radio control but can't remember now. So I was told that it can come up by a false radio signal.

The dealer is talking out their ass... it doesn't work by radio frequency. It works by tire rotation. The computer counted the rotations per minute by each tire and compares them... if one tires is soft, it will rotate differently. After enough difference in rotation, it throws the light.

Wheel rotation is calculated by ABS wheel speed sensors. If a wheel speed sensor was faulty, it would through an ABS light.

Originally posted by Kevlar
The dealer is talking out their ass... it doesn't work by radio frequency. It works by tire rotation. The computer counted the rotations per minute by each tire and compares them... if one tires is soft, it will rotate differently. After enough difference in rotation, it throws the light.

Wheel rotation is calculated by ABS wheel speed sensors. If a wheel speed sensor was faulty, it would through an ABS light.

Kevlar,
I agree with you. I thought it was working by the same principle you describe and I guess we are right and my dealer was talking bulls%&t as they were doing most of the time.

Well, it's possible that the tire pressure warning could trigger without throwing an abs light. The tire pressure monitor works only by monitoring the difference between the abs sensors on the wheels, not whether or not the wheels. If one sensor was returning a slightly "off" value, it could very easily not be within tolerances for indicating a braking system failure but could easily indicate a low pressure tire.

Just try to imagine when you lose a couple psi in one tire.. its rotation speed isn't *that* much different than the other tires.. maybe 2-5%. If that kind of a difference threw the ABS sensor entirely, then the ABS light would throw whenever the tire pressure light lit also!

I just wanted to point out that i've experienced the same problems at random times... although it does not happen often, when it does, it happens most frequently on bumps. There have been other occasions when it randomly goes off.. and then there was this other time when i tried to do something stupid like powerbrake....... and this other time i tried to dyno my car (which didnt work even with the codes i've seen posted on here) .. my point is this: it's pretty much random so don't pay too much attention to it.. check your tire and if nothing is wrong, reset the sucker. As as aside, Kevlar, that sig is sick bro! nice one...

The tire pressure warning light is set off by the presence of a variation in the rotational speed of the wheels. So if you hit a bump or anything happens to cause a difference in the reading between the four wheels, the light may come on and then reset.