What would cause an ECU to burn out? My brothers mk2 VR6 (2.9 corrado engine)

was running fine, but then started getting progressively worse over a few weeks, with a misfire, until it wouldn't start.

Opened the ECU up to find this







Now, the ECU was not bolted down , and this is right in the middle of the board, and it was in the engine bay so could possibly be water getting in there?

But to me, it looks like the chip has overheated, maybe down to a sensor/ loom fault? What do you reckon, as I don't want to replace the ECU only for it to fry again?

 

short i would say but having said that once a short is in the circuit it would fry it quickly rather then being progressive time to do some resistence checks from the ecu plug to various sensors (after inspection of the loom )

 

Nice car!!
Good that you've found it anything could of happened there

 

if the chip had overheated it would be a smouldering mess in the middle or on the chip. looks like something has got alot of current flowing through it.
looking at the board you normally get the evidence of water ingress somewhere, as its right in one place it looks like something was pulling far too much power.
not much help i know, sozz

 

I will try not to get too technical, but I graduated in microelectronic control engineering a long time ago and old habits die hard!

the printed circuit board (PCB) in that ECU is multi layered. this allows tracks to go in more than direction. There are little holes in the PCB which electrically join the cracks to complete the circuits, these use solder. Also there are to more than one type of circuit, some are higher power some are lower power, If dirt gets into a cracked or "dry" joint (dry joint is a type of badly soldered joint in which the solder failed to wet the metal. These are liable to fail electrically) a resistance is created and therefore a voltage drop, this creates heat focused in a very small point, leading to circuit burn out as the tracks are thin and so are the layers of PCB. This can also happen at any join on the PCB too.

Regarding you other question the power circuits are fused to to stop an electrical fire in the car but this will not guarantee circuit overload in a PCB on the ecu of a sensor has shorted out.

hope this helps.

 

Maybe BBA-Reman or similar ecu repair place could repair the ecu and also give an indication as to the cause ?

 

I don't think it's repairable to be honest, proper crispy fried ducked . They are not too expensive anyway, £60-70 I think from eBay.