Ditto what herb said with 1 possible exception. Certain faults are corectable via software download. Others require replacement of the ETM. There is a tech net note available to the dealer via the vadis system which is very specific on which codes can be corected by download and which require module replacement. And yes, most dealers have a handfull of incompetent techs. They also have experienced, caring techs who take pride in their work. If you don't trust your dealer, check with another one for a second opinion. Find out what fault codes are stored in the ECM/ETM and repost.