So saturday i tune a 9n3 polo gti with bjx engine with my genuine kessv2 master

Get it running good and fine without problem. Sunday I go to check on the car and adjust the tune.

Write new tune to ecu through obd. All good
Start car, All good. Rev car a couple of times and its fine but rev it again and the car stalls out and refuses to start. I then tried to write the original file back to the car but kess cannot read or write through obd.

Take it out and put it on the bench to boot mode it and i can read and write in boot mode fine. Read the file and it all checks out. So i write the original oem file back to the ecu and put the ecu in the car and still nothing. Car will not start, cannot read or write via obd.

Took the ecu + a spare me7.5 ecu to a local tuning shop and got them to delete the immobiliser and also put the original oem map on my spare in case there was a problem with the circuit board.

Neither ecu works, car still wont start and still cannot read or write via obd.

Checked every single fuse. Checked the loom connectors on the engine bay side and still come up with nothing.

So,

Any ideas?

Yes i did as i dont know how to take immobiliser off.

Turns out it was a fuse after i took them all out 1 by 1 and spotted it. Hasnt blown since, very strange.

During this fiasco and speaking to alientech and them telling me no idea i did start thinking a tool issue but no a blown fuse "Ignition transformer" caused all my headache. Live and learn