Originally Posted by onehundred80
Maybe your battery has a hard time holding a charge or the alternator is producing enough power. So when you reduce speed for an extended time the power used is more than the power generated or held, resulting in a red light.
It could be poor connections at the battery or the cable to ground or the alternator. How old is the battery?
I don't think the speed is a factor in this case. It's a major highway project and although there's a lot going on speeds are 60-70+ mph. It doesn't happen when I drive on the back roads closer to home where speeds are reduced.
The battery is a 850 amp Bosch that's only been in the car for about 6 months. I'll have that tested if the alternator proves to be OK. I'll also check the cable connections in case they're moving due to the rough surface.
Reading through other threads I hadn't seen interference problems discussed. I'm trying to cover as many the bases beforehand knowing that trial and error can take some time.
additional - there was no code on the OBDII reader when this occurred.