HJ80 landcruiser ABS fault

hi all, i am looking for ideas about an ABS fault on my dad's HJ80 landcruiser.

the problem...
-ABS has always worked just fine
-several months ago, i personally took the air con blower box apart from under the dash, to remove the grass the mice on his farm had so thoughtfully deposited there.
-the only electrical thing involved with that was disconnecting the plug which powers the fan.
-when i put it all back together, the ABS light was on, and has been on ever since.
-it isnt just the light - the ABS does not actually work, it has had a 4WD specialist where usually serviced, attempt to fix it, and a Toyota dealer attempt to fix it. neither of them has any suggestions other than 'replace the ABS'..

i cant see how disconnecting a plug which powers the fan could be the problem, but the problem appeared at that time, so let's not discount anything! however, that leaves the problem of why the light is on all the time, the ABS doesnt work, and why professional mechanics cant figure it out.

does anyone have any brainwaves on the subject!?

thanks in advance.