While out cruising in my new to me C5 Anniv. Edition Convert. today, the check engine light popped up in a 'fixed on' position .... at the same time I noticed that the speedo was only hitting 50km max regardless of speed .... is it possible that these things happened at the same time as a coincidence, or is it possible that there is a sensor somewhere within the engine works that ties these two items together ? .... tach operates ok ... engine runs fine otherwise ... car only has 58k ..... my first issue since purchasing 1 yr. ago .............. looking to the experts for ideas ? ......... Thanks