HI We have this truck serial B460T01553H, i had this problem nearly 2 years ago and left it due to not being able to find any information for the wiring checks.
Went to the same site today to repair another VNA and they asked me to look at this again.

The display on the truck shows error on MOD 06.
When we plug our zapi handset into MOD 06 steer unit it says on the dsiplay 'D Line Sensor KO.

The generic zapi EPS book states the following:

This alarm occurs when the mean voltage on the Direct line of the stepper motor (connection CNA#9) is not null: the voltage on every stepper motor line is a sine wave with null mean voltage. - Remedy: Check the continuity of the stepper motor connections. In particular the resistance between CNA#9 and the minus battery (stepper motor at rest) is expected being very low (close to 30 ohms).

If anyone could help with a manual please or even a wiring diagram this would be really helpful. Or perhaps advice on what else to check.

Thanks in advance.