mine as well started to read about 10 kmh less than the actual speed. Then within a week the 'error' has increased and is now reading about 50 kmh less!!! So basically at when idle the needle goes backward and is presently indicating 210KMH, instead of zero!!! This is a very common problem in Peugeot 206, think u'll have to replace the whole instrument unit. You may get one from ebay, but make sure it's exactly similar to your present one (1 plug or 2 plug). Or you may try to replace the stepper motor inside the unit if you are a handyman, which will cost less.
juneid
December 2010