a8lonyour6

Hi all,

I'm brand new so thank you for allowing me to join.

I had to jump my 2005 A8l, 4.2 because of an occasional/weird battery drain.

Got the car started and plenty of juice in the battery, however, the "flat tire" dash warning light came on. I went into MMI to see what was going on. Under "system" the interface indicated the system was "off". Turned the system on and it instantly switched back to off. I've tried this whilst the vehicle was running as well as turned off and on every occasion the MMI reverts the TPMS to off with all the other options greyed out (reset pressure/store pressure)

Any thoughts?

91quattro

Could be the module is bad. What is the age of the tire sensors? Those batteries don't last much beyond 5-7 years IIRC.

the_duke

How did you connect to jumper cables? The picture below shows how they must be connected(positive on the battery and negative on the ground post). If you connected them directly to the battery you most likely caused an issue.

a8lonyour6

Connected as shown above.

I'm not sure about the age of the TPMS baterries as I've only had the vehicle for 4 years, however, I'm not sure that failed batteries would disable the system function in MMI.

Any other thoughts?

the_duke

Failed batteries will not disable the system. These cars can be finicky. Personally I'd never jump start someone using my D3. They're just to prone to these types of issues. But to try and help you the only suggestion I have would be to disconnect your battery and leave it that way overnight. You might even want to put a battery charger on it overnight while it's disconnected. Also check the fuse for the TPMS system(I have no idea which one).

Another thought. Make sure that tiny wire you can see in the picture is still connected to the positive terminal.

Beyond that a VCDS scan might reveal what the problem is.

enGage

I'm going thru the same issue. When I put new tires on a few years back, I installed aftermarket sensors. They worked fine most of the time, but once in awhile they don't read. I've been getting the TPMS warning for about a week now and when I check the tire pressures there is no reading on any tire. It's unlikely that all my batteries went out at the same time. I'll check the fuse and disconnect the battery and see where I get.

MP4.2+6.0

Doesn't compute--about the 4 years. As a 2005, original sensors long dead w/ max life of 5 to 6-1/2 years. Who knows when last replaced. If like 2011, they clocked out again perhaps.

Also, if spare sensor goes down, it can take out rest of system, and from experience especially if one of the other rear wheel ones is already weak. With VCDS you can see which one it is, and estimated battery life. That's really how you figure out down to wheel level what is up, especially with aged (or unknown age) sensors. When a sensor goes on blink, whole display goes blank as far as temps or pressures if that is what you are (not) seeing.

enGage

So you are saying that if one goes bad/looses battery, all the wheels stop registering?

MP4.2+6.0

On the screen display, yes. Thus, you won't ever see a display with 3 tires, but not the fourth. The spare is an exception where it can show that as blank sometimes, but still show other 4 road tires.

You can still "see" them with VCDS unless battery goes to absolute zero, but then VCDS tells you by wheel which are fully MIA. Sometimes when they are in throes of dying, you can reset display in MMI and get them back for a while. They first seem to start acting up when they are in later life--or at least did for me--when weather gets cold, especially like ice/snow on roads cold. Mine first did that on a drive to Aspen. I got them back in warmer climate, but within a month or two of winter in a milder climate they blanked out again. Mine was at end of CPO warranty back then, so Audi actually bought me a full round of sensors.

Doc_A8

Ok, hold on... in your MMI you can switch your tpms system on and off? How?! I thought this could only be done via vcds? I'd love to be able to switch mine off or on at will.