Issue with Main Body ECM
 

Hey guys,

to put this into context, i have a 2013 BRZ Limited with keyless entry.

A while ago, i had a short with my reverse light and it caused the stop fuse on my main body ecm (fuse box in driver footwell) to burn out the contacts. This lead to me purchasing another whole new off ebay and I believed all of them are the same. So I installed the whole new box and everything seemed to work, brake lights, taillights, radio, ac controls, etc... but it would not start my car! It didn't detect the key at all and i couldn't lock my car. I then did some research and it looks like there are different ECMs for different models of ignition and different key types. So I took out the new whole box i bought and put in my old one, car started BUT now all the accessories don't work! The Taillights/Power Steering/Brake Lights/Radio/Heater Controls/etc all dont work! However, the car starts. I don't understand this at all. I couldn't find any blown fuses after looking for them on both the engine fuse box and the interior fuse box. I really am very confused and frustrated. Maybe I have to reset something in the electrical system? I tried disconnecting my battery for a long time and still nothing, I pulled the engine ECU fuse, nothing. I'm not sure what to do at this point. It's so weird to me that the car is detecting the key from the ECM but now none of the fuses wants to work, I even tried replacing the ECMs with both fuse boxes and same thing, doesn't work. I know this is a bit farfetched and a very unique issue but I don't know what to do anymore.

Send help pls thank you!

seems like immobilizer issue. you have to get key matched.

I would think the immobilizer would prevent the car from starting, however it starts perfectly fine.

I'm having body ECU issues myself and a buddy who works in a dealer service department told me that when changing it out they have to program it to work with the car (to make it play nice with the other computers, I assume). Maybe that is what's causing your issue?

The new one didn't start the car because it is not paired to it.
The old one will start it since it is paired but nothing else works since it is fried.
Need to get the new one paired so it both starts the car and runs everything.

Nope I found it out, the main fuse on the positive terminal was blown. I probably accidentally hit the positive terminal with a ratchet as I didn't have a cover on. Ordered the part from Toyota. We took a soldering iron to the fuse and then started the car and cleared the DTCs and boom, was like brand new.

See above post,

It was just a fuse on the positive battery terminal. I tried after and all of the combinations with the old ECM and all the fuse boxes it was attached to worked after.

Did you put the new ECM into comms mode by looping pins 4 and 13 in the OBD port and leaving it for 30 min?

It was not a new ECM. It shouldn't have had any affect on anything. The issue was that the 140A Fuse on the Positive Terminal was blown. Probably from me accidentally hitting it. Causing the Alternator to not charge the battery as well as all the ECM/Fuse Box issues.