Tyre Pressure warning light E 46 M3

[dadofbud]

As the title my warning light keeps coming on, I've rerest it several times, I have searched this forum and many others, but can someone please be so kind to explain how where and why this system works or does not in my case.

I really don't want to go cap in hand to BMW dealership, so would greatly welcome your collective help in resolving this anoying problem.

Thanks

Bob

[MrOnTheRopes]

Assuming your tyres are fine, have you recalibrated it (as per the handbook)? or are you just making the light go out (temporarily) by pressing the button?

[dadofbud]

Sorry should have more specific, tried the recalibration and as deatiled in the owners handbook and and as detailed on other fourms even got someone else to do it just in case I missed something but it just comes back on !

[simple simon]

i wonder if one of your wheels is not quite true ? minute vibrations ?
i have 2 sets of wheels one dose exactly what you say the other dose not ?

get them checked out budy !!

[gavm5]

have you had new tyres fitted ?

BMW main dealer offers free tyre checks - get them checked first.

the tyre pressure monitor works by measuring the rolling radius over a set distance.

if you have "run flat tyres" they will still look inflated.

Edited by gavm5 on Tuesday 18th November 20:52

[ian in lancs]

I assume the Z4 is the same and the UK early ones work like this....

On each wheel is a toothed ring. Each tooth triggers an ABS sensor as it rotates past it. Thus no signal - wheel is stationary. Pulse signal, proportional to wheel speed is used by the ABS to detect locked wheel(s) and in the tyre pressure monitoring system it compares the relative wheel speeds.

Where one wheel speed changes speed (IIRC increases more than 30%) relative to the others, pressure loss is assumed. That triggers the alarm. I guess the software is quite clever to prevent spurious warnings but I'm sure you get the idea. IIRC on later Z4's, or maybe just the USA ones, the ABS approach is replaced with dedicated sensors in the valves but I don't know how those work.

ETA resetting it allows the system to learn the individual wheel speeds for a given true speed - canceling tyre wear variations and the like. Thus is only triggers on difference between wheels. If all four tyres went at exactly the same time, unlikely, I guess the system would assume the car has just changed speed rather than a puncture.

Sounds like you have a dicky sensor or loose connection(s) they are exposed to the elements. What about talking to that German parts supplier GSF to see if its a common problem. Maybe there's an error code stored and if you're lucky an indication of which wheel is triggering.

Edited by ian in lancs on Tuesday 18th November 21:18

[dadofbud]

excellent and many thanks, i have changed all four wheels for original csl's ( all correct part codes numbers ) going to investigate the error code route and see what this brings up with a view to further investigation of faulty sensor or bad connection.

I may put my original 19's back on reset and see if it happens again

thanks again

Bob

[ian in lancs]

I doubt changing the wheels will make any difference - the toothed wheel is mounted on the back of each hub

[MrOnTheRopes]

ian in lancs said:

Sounds like you have a dicky sensor or loose connection(s) they are exposed to the elements.

It's less likely to be a faulty sensor (wheel speed sensor) as they're used by many systems - eg, ABS, DSC and SMG if present - so if one goes down you get dashboard fault indicators for all those systems.

[Pork]

I had the same on mine and it turned out one of the wheels was ever so slightly buckled. It would go off for 10-15 mins, but never lasted.

Hope you get it sorted.

[oli_quick]

I'd firstly make sure you are driving off after reseting the sensor...as I believe the rotation of the wheel is important.

Also review what temps you are reseting and then having an alert at - this obviously effects pressure and can cause system alerts...