ABS brake light, cruise control does not work when headlights are turned on

check ground for battery to body, and engine , rear ground on rh quarter panel or trunk if sedan and finally check battery for condition including load test as well as terminal end cleanliness and charging. most places do the last for free, if none of this works have amechanic scan for codes.

Thanks for reply. I have been working on this and other electrical problems with this particular car since I bought it with 56,000 miles about a year ago. I see on the internet that many others have had the same problems over the years. I have conducted all of what you suggested and the battery is new. Diagnostic code says brake light switch and "B circuit". Changed switch. Same code. Cleaned body ground on cruise control module and added a wire body ground to CCM. This got CC to work but only when lights are off. Once lights are turned on, the CC and ABS systems malfunction until codes are reset. Will report when I finally figure if out.

if you replaced parts a scanner has to shut off the codes which mechanics are normally the ones to do this, but this sounds like a ground problem of some sort. check battery to body ground at body and engine.