Quote Originally Posted by RinconVTR View Post
May be you've heard stories like this...but its not a fact.
Actually there are quite a few ranging from at best older ECM's that had a low amount of Keep Alive Memory and no lithium battery back up where you would have to drive the car through a learning cycle before full drivability was restored to some models that dumped and required reflashing of the memory...

A good mechanic will use a 9-volt battery connected to a cigarette lighter plug to hold the ECU memory and Radio Presets when the disconnect the battery.