BAS ETS Warning Light
 

I have a 99 E320 4Matic. This warning message came on about a month ago and then disappeared. It re-appeared this morning after a very cold night. Could the cold be affecting the sensors that trigger the message?

One other unrelated question. The outside mirrors have an auto dimming feature. The passenger side outside rearview mirror jiggles constantly at night when headlights appear in it - almost like it has a nervous tic. Where's the sensor for the mirror? Difficult to replace?

A drop in battery voltage below a certain level can cause that to come up.

Thanks for your suggestion. The warning light went out yesterday but came back on this morning. As the battery is still the original, I'll get a new battery.