I am having problems with my transmission so I got a new transmission relay and a different ECU from a junk car.
I have tried 3 ECU units from junk cars, all with the correct part number, but none of them will even start my car.
When I am changing the units, I have the negative battery cable disconnected. When I unplug my ECU and plug the replacement unit it, I hook up the battery but none of them will do anything but crank the engine.
I then disconnect the negative cable and plug my ECU back in - fires up every time.
Do I need to "reset" something to use a replacement ECU?
Thanks.

 

cant just "swap" ecus. All need to have keys registered to the immobilizer ECM.


assuming you have a 2000 or newer, since you didnt say.

 

ditto. gonna have to tow it to the dealer

 

i replaced my ecu (explain start to finish) i checked the numbers with the old one (the one that was factory) they matched if they dont match its a no go ... disconnect old one disconnect ground (battery) or youll possibly fry your ecu plug the new one in connect ground turn ignition on (dont turn over ) turn off take key out disconnect ground then disconnect hot wait 2 min then place hott, ground in that order and start car check your dash lights after 30 sec see if any unexpected lights are on ....... thats what i did and it worked another option you can use is go to advanced or any auto parts store and grab the haynes manual for your car only 19.99 maybe a few and maybe less and that will tell you step by step from tear down to rebuild also overhaul