Hello, So i had a battery on the car, everything worked, all was good. I took the battery off because my friend needed it, a month later i put the battery back on, and i go to turn on the car, but none of the electronics worked. No windows, radio, ac, turn signals. Only the hazards worked. Also, all the lights in the dash were on. So i checked all the fuses and relays, all was good there. So i decided to take the battery off, and take out the ECU, bought a new one and replaced it. It claimed to be working but hen i installed the ECU again, put the terminals back on, the car won't turn over, but i sounds like its about to and then just stops. And all of the electronics still don't work. I put my old ECU back and he car starts, but same problem. I tried connecting an OBD computer to the car while both ECU's were on, and the OBD won't start. Anybody know what to do?

 

Start with the basics first!

Have you had your battery load tested to make sure it is still good? Electronics can do weird things with low voltage especially with newer cars.

Check the condition of the battery connections/ cables and ground connections and clean them off so you can make the best connection possible.