On my old S420/1998,the BAS/ESP light will come on and stay on at start up.The problem is that the car will stall while waiting at the light,or lose and regain power on occasion.I don't know what relay is responsible for the BAS,the heater blower is dead,that might be related if those two are wired thru the same k30 relay or fuse?I thought about the brake light switch,however,the W140's don't really have that problem...

Will it stall at the light or stop if you put it neutral or park(foot off the brake).

You may just have a vacuum leak on the brake booster. Their is a brake pedal linear travel sensor on the brake booster it could be bad or leaking from there. You have to remove the ring around it, so it slides out.

First things first, read the codes, and see what you get.

Martin

There is no brake booster leak,its electronic,however,I don't know where those BAS/ESP relays are....