Bingle

Last time my car was in for service I got the flat warning on the way home. I had recently bought new rims/tires so I stopped by that store and was told that my car ('06) isn't monitoring tire pressure, but is monitoring changes in ride height from the suspension. Since the car had been in for a new rear suspension compressor that made sense - no more warnings after resetting.

TwoPedal

Thanks, Bingle. Service did install a new module that controlled ride height. I hope that was the problem. I reset and haven't had any issues since. At first I was worried they lost or damaged a tire sensor.

Bingle

Question for you - does your car have TPM sensors? Evidently mine no longer has them and as I mentioned above, I was told it was now a function of ride height. I switched out the original 17's before really looking for them.

TwoPedal

I'm assuming I do. When I go to that menu there are options (calibration, on/off, warnings). Also when the alert went off that night is said, "Tire Pressure Loss". Since I was having issues with a module that controls among other things, ride height, service wiped the iDrive and installed a new one (all my settings vanished.) I assumed that the TPMS lost its calibration and assumed a pressure loss. My wheels are the original factory installed ones, so I'm hoping the sensors are still there. Without a definitive answer I'm sorry I can't answer your question with any certainty.

To what wheels did you switch? I have browsed oem BMW wheels, but it seems like every style I like has a note that they will not work on Xdrive cars. Is there a list I'm not finding?

Bingle

Yes mine gives the same warnings and has the same iDrive reset option. I assumed I had sensors in the tires until I was told the car used ride height to give flat tire warnings - I now just have the plain rubber valve stems but still got the warning. I am curious as I didn't inspect the stems before switching wheels. I went with aftermarket wheels but there several OEM alternatives - do a search here and you will see quite a few threads on the topic. The main issue is the offset requirements for the Xdrive as I am sure you have discovered.

TwoPedal

You inspired me to look at my valve stems. I have one metal one with a bump at the end and the rest are traditional plastic. I thought the DOT forced all cars sold in the US for MY06 and later to have TPMS (which I would assume are the tire mounted style). Are you sure the valve stems are the giveaway? My XC90 has regular plastic caps and uses a sensor mounted next to the tire on the inner side of the wheel.

I wonder how accurate ride height monitoring is for determining tire pressure. Gas, passengers, luggage- it all fluctuates. When the warning went off, I was on level ground on a very smooth road. Odd.

Thank you for the wheel info. I'll do a search. I was disappointed at my initial search but now I know what to look for.

Bingle

I honestly do not know and am just going by what I was told by the folks where I bought my wheel/tire package (a high-end dealer here in Atlanta). I will inquire further when I need a rotation - maybe some of the more knowledgeable members here can offer some clarification. I will say this - I was getting random warnings before having the rear suspension compressor replaced - none since then other than the one right out of the shop.

TwoPedal

With both of us having one warning right after work on compressor/height modules it seems to form a pattern. I'll ask my service department later in the week. I feel like I've been a thorn in their side for the past week- but finally the car drives and sounds like its suppose to.

While I'm posting, I have a tech question for you. After the car's been sitting for a few minutes or all night, when I unlock, open a door, or even press the rear window release button, a low electrical noise comes from the bottom of the car, almost like a solenoid or something is moving. I'm sure its normal but I'm wondering what it is. I like most of the tech in this car but some of it makes no sense- like why the NAV DVD stars spinning when I open a door. I don't have Comfort Access but I guess the car is just getting ready to be turned on. It makes me worry about the battery since I may open the doors several times a day even though I'm not going anywhere.

Bingle

Same noises here - it's my understanding that this is related to the air suspension preparing to make an adjustment. I've had some strange things occur with some of the tech as well but am trying to ignore them so maybe they will not manifest into a problem...

TwoPedal

Glad to hear its not just my car. Perhaps you could fill me in a bit on the air suspension. My technical knowledge is limited about the e61. The manual states that the rear height will usually sink down when parked. Is the entire car using air suspension like the doomed Mercedes AirMatic? or is it just to level the rear? My XC Volvos use Nivomats to do that without a compressor. Is this just a case of German over-engineering or something more encompassing?

I try my best to ignore some of the tech oddities as well. So far I have not come across too many and other times it was user error, like when my active lights were bending and I realized I didn't have the knob set to the left. I reset the transmission yesterday and the car acts like a new car. The factory settings are much better than whatever it had learned over the years.