Adaptive cruise control

[EChas3]

My 2006 STS 1SG w' ACC works great. I wonder if the plain plastic grille used on early STS help with ACC. Does anyone know of the brake lights come one when the ACC is braking?

[tedcmiller]

The rear brake lights (I am assuming that is what you refer to) should come on either with normal braking using the brake pedal or ACC braking. It makes no sense to not turn them on with ACC braking. Most newer vehicles use a pressure sensitive switch in the hydraulic brake system to know when the braking system is activated. So, I am assuming that the brake lights are activated for ACC braking just as they would be for normal braking.

Since the ACC braking should occur only under the specific circumstance of a moving vehicle approaching a preceding vehicle, you would probably have to have someone follow you in another vehicle with some sort of signal system between the two vehicles to coordinate when ACC braking in occuring and the brake lights actually come on. Another approach might be to set up a jury rig system that would allow you to see the rear brake lights while driving.

[tedcmiller]

Echas3,
I took a look at the factory service manual for the 2008 DTS with ACC and found the following statement on page 9-33:

The DSCC module requests brake light activation during automatic braking.

DSCC stands for "Distance Sensing Cruise Control" and the DSCC module is a part of the ACC (Adaptive Cruise Control).