I was just wondering if someone could explain to me why when flashing an ECU to use in a car, in my case an 04 GTi 1.8t, the eeprom from the old ecu has to follow to the new one? What does it reference? or what references it to confirm a match? Also, can you just code the vin/coding/del immo to make it compatible? or does it have to be identical code?

Also if someone might have any insight on my issue. I recently lost power while driving. I went to read codes and straight away noticed I had no CEL light. So I assumed my ecu popped or main relay, etc. When I got my car home I checked relays, unhooked 02 sensors, etc. Nothing still. So I pulled my ECU and found corrosion in the connector.. I attempted to clean it and replaced the connector seal[it was ripped....], and reinstalled it. I saw the CEL light, no start, no more CEL... after a few minutes with key off, then on again, I could see the CEL light up. As if it faults out and fails until soft reset[or cool down]. Sometimes when I turned the key on it would light up, but almost a minute after key on..

So I grabbed a spare ecu and my bench cable and tried to pull the eeprom from my orig ecu. No Comms at all, not even in bootmode. So I pulled the eeprom chip and swapped it into the spare. For info, My orig was HS, spare is HF. Tried the new ecu and still nothing. New ecu with old ee chip with immo off and HS tune flashed. Before I took it to my car I could read it from bench cable in VCDS. Now the new ECU is NO COMM as well??

My question is if anyone knows of a situation that would or could damage the eeprom chip itself and cause the ecu to fail? I use a hot air station and have plently of exp swapping chips so Im confident I didnt damage the chip during swap.

one more question if I could. I have a bunch of 8e0 audi 1.8t ecus. Could I flash ee anf tune onto them without issue? I dont know of a reason I couldnt but I want to ask in case there is any addition hardware or parameters that would prevent it. Thx in advance.

ok, so the eeprom has to match the ecu, not the flash? Or is that only in the case of using the 8e0 ecu? In which case would I be able to flash my HS tune to the 8e0? Or is the hardware difference just going to allow me to immo off and run what was on 8e0 ecu or 8e0 tune?

I do have the orig eeprom somewhere. After a few days I remembered the ecu I tried was one of the ones I got that didnt work. Which confuses me bc it did work enough for me to pull/push eeprom and flash in obd and bootmode. It even nearly started the car... Then it failed again. I eventually found a compatible ecu from my pile and flashed my HS tune and used a virgin eeprom and got my car running again.

My orig HS isnt getting voltage to most the board when compared with a known good ecu. Would you be able to tell me if this chip is responsible for power regulation? I think I rem reading it somewhere. The only schems I could find were block diagrams and it difficult to try and follow the traces. :|

thx for responding.

Don't have an ME7.5 on hand but as far as I remember you've got the right IC.

It has a thermal plate underneath for cooling which sits on a blob of solder so you need to loosen the blob up to get it off the board. A simple method for me is to get 2 HOT irons and place them in the indents on both sides of the chip on top of the plate and patiently wait until it wiggles loose. Obviously you need to lift the legs first. The board sinks a lot of heat so it takes a while to get up to temp.

If you have a rework station that works well too. Be very careful if you use a hot air gun, the amount of time it takes to get up to temp makes it easy to bubble the board.