Electrical problems

Hello, I have a 2005 GMC Yukon xl. After I go to a
carwash the electrical problems start.The abs light
is on so the brakes. The battery goes from 14 to 12
then to 16 and sometimes goes to 9, so does the
fuel temperature and oil, always playing. I’ve been
to teton motors paid 2700$ and they replaced some
sensors and said it’s all good. But nothing changed,
and then after a day or two everything works fine,
and then starts again when I go to a carwash. Does
anybody know what wires are exposed to water
that I could check. The battery and the alternator
were also replaced.