4WS Problem - Code 41

[Celica_XR9145]

Hi all, to start off with, i bought my 1990 toyota celica gtr 4ws (st183) and it came without the speed sensor ring on the left hand outer cv for the 4ws.
What happens is the 4ws light comes on after a few minutes.

It came up with fault code 41 - speed sensor.

So took it to the mechanic and he was the one who found it was missing the ring.
So we went to toyota to get a ring and the only ring listed for the gtr 4ws was the ABS ring which he says these 4ws and abs parts are interchangable.

So the mechanic fits the new CV with the ABS ring and check thats the speed sensor its self is working which was fine.

The problem is the light still comes on and everything is fitted.

What i wanted to ask is has this code got be be cleared or something?

Also, does anybody know how many teeth the 4ws ring is supposed to have or even have a pic?
The ABS ring has 48.

Also, can the ECU be modified to either cancel 'Safe mode' or turn safe mode into 'sports' mode so the rear wheels turn right?

Many Thanks,
Jamie