Brakes: 850: ABS help please

[ss2115]

We inherited a low klm 850 sedan from a relation. It had been standing for long periods unused and is in excellent looking condition.
Once it started to be used after we got it, some problems have cropped up and mostly dealt with except for the ABS system.

All four calipers were completely overhauled as they were stuck causing the car to dive left and right. Fluid all completely drained through and all flex lines replaced for safety sake.
Car brakes really well but always has a tiny initial dive left and then straightens up. After investigating for a while, the shop concluded the ABS pump was probably also jammed or frozen somehow as the fluid to the right front caliper was slower moving than to the left caliper.

The ABS hasn't been working which we knew because you can lock the front wheels up quite easily without the jabber jabber of the ABS operating. However, no fault light and no fault codes. The globe is okay as its seen on the ignition on self test.

So eventually we found a good condition ABS pump which we swapped in this weekend. Bled the system out again. Car now has a slightly more travel pedal but brakes dead straight - no pull at all.
BUT - still no jabber jabber from the ABS. Brakes lock the wheels with little effort and the car really brakes hard to a stop. Great. But no ABS, and no warning light and no error codes.

We're at a loss.
I know its common for the module to fail but everything I've read and know is that the ABS light will illuminate with any module fault. Its even supposed to light if the ABS fuse is pulled. And also often the speedo stops working. We have none of these problems.

I'm wondering about the long skinny black relay that the ABS motor is plugged into. Could it perhaps not be firing the motor but the control module thinks it is? ie: is there any feedback from the motor to tell the control module its working. There are two blue wires which "may" be feedback wires - I don't know.

I'd like to get the ABS working as my son drives the car and its safer in the wet for the ABS to be working. He'll have a better chance of steering out of trouble.