I purchased a 99 van from a lot. It was explained to me that the guy who traded it in did so while it was getting a new trans. i bought it and 2 days later on a short trip (100 miles) the Check trans caption flashed as well as the O/D light and the engine light.
Took back to the place who put in the trans and he said it had a lazy valve and put additive in it. I had it flushed after 400 miles and took it to another shop. He said he believed that it had the wrong trans. i then took it back to the original shop and they crossed the numbers and said NO it is the right trans but the converter was the code and it was under warranty. they replaced it with a new one. the shop was driving it 2 days later and the battery died and required a jump so he put a hand held unit on it and drove it 2 more days. he got the check trans and charging system light he had NAPA check the battery and it was good but the car wasn't charging. he noted that the lights came on in what appeared to be a power surge. he replaced the alt. but the the light came on again and it quit charging. he then put my old one back on. he called me to come and get it after all this and having it for 6 weeks. still not fixed cause on my home the check trans light came on again. he said he thinks this is a comp problem. He was very confident that the trans was right and fine and the alt was good but after a surge lots of codes come up and it quits charging P1116 ,P0741,P0401, P0171, P0174 And now the check charging system
Do I need to take to a dealer or just a good mechanic
rodney

 

If you go to a garage with it make sure they have electrical experience - or they'll just replace the whole deal piece by piece.