My 2018, G56, Ram 2500 has 36,000 on it. I've had service ABS/ braking system on for over a year. Call mother mopar and the ABS modue and HCU is on national back order for these truck indefinatly. No one knows how to fix it, people have had mopar dealers install new parts and the problem comes back. These ABS/traction control lights will come on and off, or stay on all the time. I found a guy on another forum that replaced just the motor on his ABS unit and fixed the problem. So why not give it a shot.
So take the drivers side wheel well out. Remove the cover on the ABS unit. Pull the plug on the ABS unit, remove the ABS control module (4 torx screws) and you will see two spade prongs sticking out. These are the leads to the motor. Put a multimeter on the leads and I read no resistance, saying the motor was open, dead motor. Hooked a 12v battery to leads and the motor would not turn. The motor is held in by 2, 12 point bolts. Take the bolts out, and pull the motor. The other guy used a used abs motor off a 2008 1500 ram. I found a 2007 Chevy Equinox ABS unit, pulled the motor off and low and behold it was the same part numbers on the bottom side of the motor. Tested the motor and it was good. This is where the pain the in *** comes. Installing the good motor. In the ABS unit you have 2 plungers that ride on the eccentric of the motor. If you reach in you can push the plungers in, they are spring loaded so there is no way to hold them while installing the motor. I went to autozone and bought the longest bent feeler gauges I could find, I used a .008 and .010 put them in the hole of the abs unit to act as a ramp for the motor eccentric to push plungers back. While holding the motor in place take vise grips and rip the feeler gauges out quickly. Then the motor will seat in place. Put it all back together and turn the key, no lights. This is the only way I have found to fix this problem, how long it will last,,,,I don't know. Hope it helps someone.