I remember an Audi a friend put a used automatic tranny in not long ago..the used tranny acted exactly like the old one!..after much "diagnosis" by a local transmission shop,they told him "the tranny you got must be "bad" in the same manner as the first one"...
He found another tranny to install in the car--but when he put it up on the lift to start the job,he noticed water dripping from the passenger side of the floor...we lowered the car,looked under the seat--and there sat the ECM for the engine & tranny,sitting in a puddle of water about 2" deep in a depression in the floor pan!...all rusted and green with corrosion!..
We went back to the salvage yard he got the first used tranny from,and the ECM was intact and looked nice--the guy was nice enough to give it to him,saying "I thought you already took it!--most of the time you need the computer the tranny was "matched" too on some cars!..
We took the seat out,plugged it in,and the car shifted perfectly..its still going strong with over 20K on it since!...
A Chevy van came in my friend shop with a baffling stalling and a intermittent "no start" condition...three other shops had given up on it...after a few days of probing wires,when we got to the ones that went thru a large grommet under the drivers seat,that went to the ECM--we found several had been rubbed thru and were broken and gangrene!..it ran great after splicing them back together...
I'd say under a seat is not a good place for a computer!...but some car makers evidently though it was!..personally I'd rather have a computer in the cab,up under the dash or kick panel--but remember GM's windshields love to leak,so make sure water wont be flowing on it..
