I believe they are referring to the trip odometer rest button.

 

Your dead right!

 

The Reset (R) button also controls the level of illumination for the instrument panel…

 

Wait, I have a 2007 SL550 and I was dismayed that I couldn't get actual tire pressure readings on the dash like i can in my 2008 S550 S-Class. You mean to say that is CAN be done? I am going to try it! It is kinda cool to see actual real time tire pressures as you're rolling down the hiway.

 

if your 2007 SL is equipped with the TPMS (USA models) then read pages 297-298 in the owners manual…..to see how it works….

 

Believe it or not - put the key in acc position and press that button three times... voilà acc battery voltage!

 

You don't say, I am going to have go try that.

 

It's my belief that even if you don't use the system to see the actual tire pressure, the system will light up that little orange picture of a tire, if and when any of the tires gets to a pressure that's outside of the accepted normal range, thereby alerting you about a problem. But being able to view individual pressures, allows you to determine which tire is having the bad day. Soon as I drive my SL I will report back on this.

 

I see this

Then after clicking that "R" button I get this:

I don't see any pressures!

 

You have the "low-line" TPMS which does not display the pressure from each individual tire. Instead, it just sets a baseline for all tires when you reset it. When the pressure goes too far off that baseline, you get an alert, but it won't tell you which tire. The "high-line" TPMS can tell you the exact pressure reading for each tire. AFAIK, there is not an easy way to upgrade from the low-line to the high-line system.

 

That's too bad! I would have loved to see tire pressure readings without having to get out of the car!!

 

Works on my '05. Try a different key position? Maybe I gave the wrong position?