Testing lambda sensors

Hi All,

I have a 1998 3.9ltr V8i Automatic Discovery, I have an OBD2 code reader but my Disco is the model that come out before OBD2 connections were in every vehichle and it wont connect to it. I think

I think have a Lambda sensor failure, without the computer I cant find out which one it faulty.

So before I spend £90.00 + on a pair of new sensors is there a way I can clean up the old ones or test the sensors somehow.

Thanks very much

John