i need to know every little thing that can cause this problem.

I have a S5 body in primo condition, but no engine. I also have a complete s4 long block with high imp injectors.

the only two s5 items I have are a OMP and alternator.

Now if I drop the long block in and start wiring it up, I'm going to have to: swap injector clips, swap alternators, and zip tie the electric OMP somewhere secure in the engine bay.

Is there anything else that will make the ECU turn belly up?

 

if the ecu doesnt recieve signal from the electrical OPM it will go limp even if hook up. so you need a S5 front cover and put the omp on. and whats is your swap N/A or turbo? anyways you need the matching ecu pressure sensor and AFM too. like if your ecu is N350 you need a N350 pressure sensor and AFM. same with turbo if is N370

 

it's a NA engine. afm, pressure, and ECU all match.

If that's all that can cause the limp, I'll just send the ECU in to be r-teked. pulling the front cover is not an option at this point in time.