I have just had a similar problem with my Renault Scenic. Its the Gearbox speed sensor that needs replacing. Part cost me £30 & £25 labour although i reckon on watching i could have done it myself if i knew what i was looking for.Its located under the bonnet on a Renault Scenic so i gather its the same for you.Its a 5 min job....no tools required just unplug the faulty one & replace it with the new one! Hope this helps.Wayne
W. Shipton, October 2006