White plug in fuse box. What's it for?

[Whysub]

I've a right hand drive 2005 Avensis 1.8vvti.  Yesterday I had a check of all the fuses and relays throughout the car(all good).  

In the fuse box to the right of the steering wheel, I noticed a white block connector was disconnected.

I connected it back up, but it made no difference to anything, so I disconnected it in case there was a reason why. Anyone know what it is?

I've tried to upload a photo but it keeps failing.

[flash22]

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