whats going on with this ABS light

I have a 2007 Volvo 670 and the abs tractor and trailer lights aren't coming on when I start the truck. but when im driving and hit the breaks ill see the trailer abs light come on with some trailers.so I thought maybe the tractor abs light died. but then I did a self test on the instrument cluster and the light pops on. and I know the abs light on the tractor should be on because I had the truck scanned for something else and the guy said you have 2 abs sensors out one on both sides.

 

Yeah I checked both of the fuses abs1 had power going to it when the truck was off. I had to turn the key on to get power to abs 2. a little background when I first went for the truck the tractor abs light was on I told the dealer. I came back a week later and thought nothing of it as the light was not on. I had an inspection and the guy said your abs light should be on as you have active abs codes but no light. I thought maybe they removed the bulb. so I did a light test on the instrument cluster which makes all the light come and both the abs tractor and trailer lights came on which means the bulbs are there.so why not when I start the truck as I have a active abs sensor fault.