Abs light. Faking it

All you need is a $6 test light. Start at the pigtail, then the harness runs to the back, in front of tandems. Then another harness plugs in there and goes to the ecu. The ecu has wired going to each sensor. Mine was doing the same thing.Except light on trailer was inoperable. Had to replace main shirt harness, going into the ecu. Get light working,then get blink code. Also had a bad wire to the sensor. Some newer trucks get blink codes on dash for trailer. Older Trucks blink code on trailers the only one. I think some older Trucks/ trailers are powered by brake circuit, instead of constant center pin.You need to identify the proper operation of each.

 

That’s right, I remember. It’s a back up supply.

 

Test the center pin, or whichever one has constant abs power on the pigtail. If you have constant power, move on to trailer plug. If not, unplug pigtail on Tractor and test tractor power pin. If no power check it at fuse panel. I’ve had to replace the 7 wire harness from panel to pigtail before on an old Truck

 

Look for the fuse to power the trailer center pin, not for an ABS fuse.

 

Don't know exactly. Isn't there a fuse/relay box in the engine compartment? Here's a picture I found that says it's from a 2015 579.

 

You're going to have to get a test light and check the center pin. If it's dead, and I think it will be, then you're going to have to run down the reason if it's not a fuse. Check it at the truck and at the end of the pigtail. Could also be a short in the pigtail.

If it turns out the center pin is hot after all, then there is a break between the socket on the trailer and the trailer ABS computer.