kd7iwp

Twice in the last month our 2009 535xi E61 has warned me in iDrive that there is a flat tire. I go out and check the pressures in all the tires and they are all correct and all within 1-2 psi of each other. I've reset the the FTM in both instances afterwards. Any idea what would cause this? The only thing I've done that I think could affect it is that I temporarily removed the front right wheel speed sensor when I had that drive axle out for my turbo replacement. Never had any codes or warnings immediately after though, first one happened a few weeks after and second time was today. I do not have TPMS and no wheel pressure sensors, just the old-school relative wheel speed system. The DSC system is working fine and there are no other lights.

audiophool

Are all the tires the same brand/size? One with a lot more wear?

kd7iwp

Correct, they are all the same type and size, approximately a year old. I wish the idrive display would tell you which tire it thinks is flat instead of just warning you to come to a stop.

JayArras

That's strange that it doesn't tell you which one is flat because when one is low on air it tells you which one.

kd7iwp

Agreed. I guess since it doesn’t know tire pressures at each wheel it doesn’t feel obligated to say anything. But seriously, it wouldn’t hurt them to show where they think the problem is.

donpb

Check your tires and if none are low, reset the FTM.

When I first bought my e60, I hit a bump and it'd say flat tire. I'd check the air pressure and all were good. So I now just reset the FTM.

FormerE30Owner

The FTM system doesn't indicate which tire is flat nor which one is low on air. The FTM only indicates that one of the tires is about 10% lower in tire pressure than than any other. This by monitoring the relative speeds of each wheel. This means that a difference of about 3 psi between any two tires after the system has been reset to register the relative tire rotation speeds, the alarm will occur.