[Boog]

I found some disheartening info in a lowly Chiltons manual.
The Kelsey Hayes 4 wheel anti lock brake system is a complicated beast. It cannot be serviced.
The Electro-Hydraulic Control Unit controls the pressure within the brake lines. The unit is made up of 2 types of valves, isolation valves and dump valves. The valves are controlled by micro computers within the EHCU. The EHCU operates by receiving signals from the wheel speed sensors and the brake lamp switch.
In a severe brake application the EHCU valve will either allow pressure to increase within the system or maintain (isolate) the pressure within the system or release existing pressure through the dump valves into the accumulators.
Bleeding the EHCU valve requires 3 special tools and a Tech 1 scanner or it's equivalent. Bleeding cannot be performed without this equipment.
It says the abs control unit (EHCU) has to be bled itself before bleeding at the wheels can be done in order to completely remove all air in the system. 15 step procedure.
These ABS control units are quite pricey. Some going for several thousand $ on high end vehicles.
A new control unit is not a viable option for this 14 yr old vehicle. I have another unit from my wrecked 97 GMC but it's the same age and I still have to have those dealer tools to bleed the system. Taking this old truck to the dealer will cost a fortune also as they will want to replace the WHOLE brake system even though many parts are new.
I don't think I can disable the ABS (plumb around it) without the dash light staying on.
So at this point I am using the truck as is until such time as I learn of a better way to get the good brakes back.