John,
In all the years working with LR i have only changed 1 D1 ABS modulator.
This was on a new vehicle still in warranty while doing a PD.
Unit was cross threaded when brake pipe went into & couldnt repair.
I would gather it is a sensor, I have read u have checked them, but we find that the sensor reads ok when testing with a multimeter, but tends to fail when the cable is bent as the outer sheath goes a little brittle in time.
You can get ABS sensors done as change over units, as there is a guy in Melb who does them. I can organise if one is needed.

