ejfiii

This is totally bogus. Can the VAG-COM enable this feature where we can see the actual pressures of the tires? My stoopid Infiniti had this and I know other cars do as well.

Also, is there a MMI firmware upgrade available for early 08 cars? My backup camera stays on for about 15 seconds while moving forward, the phone sometimes shrieks for a split second while dialing from the phone itself and pressing send, and finally and most importantly, my BB Storm will not stay connected to the system. Sometimes I have to delete it in the MMI and re-pair from the phone twice a day, other times twice a week.

Finally, if I make changes using the VAG-COM does it get reset at each service where the tech sets it back to factory fresh or something simple or would they have to reverse each change individually?

Thanks very much guys.

HoustonA5

The TPMS system does not physically check the pressure. It monitors the rotation of the tire to determine if there's been a pressure loss, so the short answer about the pressure is NO

There have been several MMI updates, the dealer can do these at any time.

The VCDS settings that you change are not necessarily reset each time. I made several changes and they were not reset in a standard 5k service at the dealer. Other have had different experiences.

pierreb

pretty sure the TPMS system in the A8 gives you the actual pressures.

Could've been the Q7's.

I forget.

HoustonA5

The previous systems did. The new generation does not. I have a Q7 and it does not tell you the pressures

kylew3

From what I understand, this is an incorrect statement. There are sensors installed in the wheels at the valve stem. Even VW currently uses this method for TPMS.

You can store your current tire pressure thresholds in one of the MMI menus while you're parked. So if the system relied on the rotation of the wheel to determine the pressure of your tires, how would the system know the current pressure if the wheels aren't spinning?

HoustonA5

Actually my statement WAS correct. The current generation, including those on the A5's are INDIRECT TPMS. Therefore the do not directly measure the pressure of the tire, but take into account rotational velocity to determine if a pressure loss has occurred. What's really happening when you store the "tire pressures" is that you're storing the current rotational information. If that changes significantly, then that indicates a pressure change.

A5_4GP

Here is a good article on The Indirect TPMS.

http://www.autofieldguide.com/articles/040805.html

It seems that is may not be available on all models yet. I found a post from Doc@Tire Rack that says the 2009 A6 is the only Audi using the indirect TPMS.

kylew3

If you are indeed correct and seem to have some inside knowledge on this subject, what is the purpose of having a ~$100 sensor in each wheel? I thought they sampled the air pressure of the tire and wirelessly transmitted the sensor readings.

HoustonA5

Read the article that A5_4GP posted, there is not a sensor on the wheel. It uses the ABS sensor to do the measurements. It's not inside information, it's just learning about the systems.

kylew3

The article A5_4GP posted is about indirect TPMS, which is not the method of TPMS the 2008-2009 A5/S5 in the US use. Instead, the valve stem in each wheel is part of a sensor as can be purchased here: http://oempl.us/index.php?main_page=...roducts_id=224

Additionally, here's a statement from a representative at TireRack on Audi's TPMS system, which is what A5_4GP was referring to: http://www.audizine.com/forum/showthread.php?t=188452

One possibility for not having the ability to view individual tire pressures is that Audi didn't develop the TPMS system to share the wheel sensor readings to other systems, like MMI.