I saw this happening at a car sale (it was a flea market for cars). some guy claimed he used to work for BMW as an mechanic, and he was interested in buying a second hand BMW 3-series. The mileage counter said 240.000 km, but he got in, stuck the key in to the ignition (not completely), pushed the brake, pushed some buttons (didn't see which ones) and suddenly the counter gave a whole other mileage: 370.00 km!!
He said the owner (who had bought the car second hand at 40.000 km) was probably ripped off himself when he bought it (I know the owner, he didn't alter anything himself) The card was second hand sold by a recognized BMW center (they had their license revoked some 2 years ago, for fraud) with 40.000 km, but in reality, it already had 170.00 km on it, according to this ex-mechanic
Has anyone seen this before? What's the exact trick to get the "real" mileage of a BMW popping up?