Was driving the 98 ML320 (123K miles) tonight around town and the ETS Light came on and is staying on. No previous issues with this - ever. I did a search and found a seemingly common cause is a brake switch under the dash somewhere. I road tested, and sure enough there is no cruise control. Is there any test I can do to test the brake switch - is it a normally open or normally closed switch that I can do a continuity test on. Also, where exactly is it at and if I do a DIY will the light reset itself or will I have to have a shop reset it.

ETA: Brake lights seem to work - I also did a search after this post and found Gilly's reply about the switch. Would a failure in the steering angle sensor cause an ETS light also?