sullyj

I have a 2008 D3 (4.2) with roughly 180,000 miles. The TPSM light came on yesterday, but all tires appear to be at correct pressure. When I try to view the screen to see which tire is low the screen has no entries for any of the tire pressures. Typically I just input "store tire pressures" on the MMI which puts the light out and go about my merry way, but after a few miles the warning light came back on. I'm thinking I have a bad sensor on one of the wheels (???). Would one sensor cause the MMI screen to show no pressure for all the tires?

Mister Bally

Yes, one bad sensor (typically the battery has reached the end of its life) will give you the yellow alert and disable the system.
Typical reported life of the factory sensor batteries is seven years.

Doc_A8

If you have the ability, you can code TPMS off.

Jack88

Swap out the sensors the next time you need tires and ignore the light for now. The part number is 4D0907275E and OEM ones are around $100. I know there are some cheaper aftermarket ones, , but I have no experience with them.

sullyj

Thanks! Anyway to determine which sensor is bad?

Jack88

It doesn't matter, they are battery operated. If one has died, the others will be right behind it. These you just do all at once unless it seems one has failed prematurely.

MP4.2+6.0

You can scan it w/ VCDS and as I recall it will tell you the wheel. You can also read the estimated battery life w/ VCDS if you think the sensors are different ages. Otherwise as mentioned, they will all go out in close succession if from same general vintage. There are 5, including in the spare. I used OE, but not dealer. The OES was Beru, which got sold to Huf. You can find them on line including eBay, Stems also sold separately for OE type.The newer versions are supposed to have some tweaks to extend life. There are also other no name ones available, some for modest $. Be sure they are the right USA (or other market) frequency. D3's had two frequencies depending on local market. USA is 433MHz IIRC. As mentioned, best to do when tires need changing anyway since they have to come off to get at sensors.

MainelyA8

If you do end up replacing the sensors, I would avoid OEwheels. They have been recommended here and there on this forum, but I've had 3 of them go out between two sets and the rest work intermittently. As per usual with these cars, go OEM if possible.

sullyj

Okay...determined the issue with my tire pressure warning light is a faulty monitoring ECU. Having spent 6K in last 30 days for upper lower control arms, new oil cooler, right side air strut and a new coolant reservoir tank, I'm not too excited about another potential $600 purchase. Should I try a used unit?

Jack88

I'd try a used one.