Acura doesn't make it clear what they want the 'S' to stand for in the D/S button. They call it both S Position mode and Sequential mode, although a more logical term would be Shift mode. It is engaged by pressing the D/S button twice, or if you are already in Drive, pressing the button again, which allows you drive the RDX as if you had a manual transmission though the use of the paddle shifters. I have found, however, a more useful function for the D/S button. When I begin my decent down a steep grade and I reach the speed I want to maintain (which is usually 72 mph), pushing the button automatically keeps my RDX at that speed with engine braking down to the end of the grade, when I then press it again to get back into Drive. All the vehicles around me are applying their brakes for many of the three minutes as I go down our local (Cuesta) grade, but I don't have to touch the RDX's brakes once. I rarely use cruise control so I haven't tried it for going down a grade, but I feel the Sequential Mode is a much safer option.

 

The "manual" mode you are describing is called "Manual Sequential" mode in the Acura literature. An "M" will appear on the MID, between "S" and the gear number, when you are in this mode.

As for "S" transmission position, that is sometimes called "Sport" mode, as opposed to "Drive" and if you dig deep enough in the Acura literature you will find that. Some people claim it stands for "Sequential" but the transmission does NOT behave in a sequential manner in this mode; it can skip gears just like any normal AT while it's in this mode. It's only sequential when you have engaged the manual mode by using the paddles. Unfortunately "Sport" is also an option in the "dynamic mode" settings.

Manual sequential mode can also be accessed from "Drive", but the transmission will resume normal automatically operation if you stop shifting with the paddles and cruise at steady speed for a little while.

Refer to pages 19-20 of the Owner's Manual:

 

"As for "S" transmission position, that is sometimes called "Sport" mode, as opposed to "Drive" and if you dig deep enough in the Acura literature you will find that."
Nowhere in the OM does it state that the 'S' in D/S stands for Sport.

 

Where did I say OM?

 

This is from the online service manual:

BTW, I had forgotten that the sequential modes can be cancelled by holding the "+" paddle shifter for a few seconds. So this digging was not for naught.

 

They really didn't handle this very well IMO. Why dedicate a GIGANTIC spot on the dash to the drive mode selection knob but also make a transmission sport or sequential or whatever mode. It's confusing for no good reason.

 

Yeah, it's so confusing Honda/Acura can't seem to decide what they want to call the different modes.

My favorite is D-Paddle. I think I had suppressed that one. With cause.

 

If in D mode, and you use the paddle shifter to downshift a gear while going downhill, it'll help hold your speed down, but then at the bottom of the hill, the "TCM detects a steady cruise" and automatically cancels the shift mode and resumes normal D mode driving. That way you only have to hit one button once. I use this all the time in my MDX...mostly while using the cruise control and approaching a hill up...the cruise alone lets the speed dip a few mph before finally downshifting then overshoots the set speed and it drives me nuts. By downshifting at the beginning/bottom of the hill, cruise maintains steady mph then automatically upshifts again as soon as the hill crests.