Wiered ABS warning light fault

[hoseman]

Got a really strange ABS warning light fault.
When ever I have passengers in the back of my 98 Ibiza 2.0 ABF the ABS warning light comes on. The brakes are fine, no ABS pump cutting in or anything.
Once the passengers get out, the light goes off.
This has only started happening since I had the front discs off to clean some rust off them.
While they were off I decided to give the ABS discs a quick wire brush while I was on.
I had the ignition on as I was listing to the radio and as the brush went next to the ABS sensor, you could hear the ABS pump kicking in.
Can't see how this can be related, its got me puggled.
I've had a look through the search engine, but can't find anything specific to my problem, though I see the ABS warning light seems to be a bit of a pain with these models.
Any help appreciated.

 

[Fl@pper]

next time they are in the back ask em to lift their butts in the air or move to one side

vagcom will show you what sensor to check

the wiring runs under the rear seats, probably a loose connection or break in it

once you turn ignition on it runs a self check and resets once driven if fault shown

 

[hoseman]

Cheers for that, I'll give it a try.