Searching for/ identifying a transistor (?) for replacement

Hi guys, my first post here. Sorry if it belongs somewhere else!
I'm trying to identify what I believe to be a transistor in the ECU on my Grand Cherokee. It's obviously been replaced earlier, as there's a different kind of silicone used to cover it. There's also a gap between the heat sink and the component with traces of cooling paste on the heat sink.
I already replaced two blown capacitors, and I plan to resolder the 60pin connections on the circuit board on Tuesday.

The transistor is marked with a ST microelectronics logo, and has two sets of numbers on it: 4392616 and below : 89109. (I'll try to add a picture here as well )
I really hope someone can give me a hint of what it is and where I can get a new one. Thanks in advance!

Why not replace the ECU module? (used parts depot)

It seems 2 failures and no knowledge of a proprietary design has poor odds of successful repair.

First of all, because of the cost. Although the ECUs are available at a fair price, shipping rates to Norway double the cost and finally I'll end up with 25%VAT on the total value, shipping included.

Second, the initial repair has been done poorly (when the component hasn't been mounted where it should be - 1.5mm away from, instead of flush with the heat sink. )

I have identified the issues, and the only thing I need help with regarding them, is finding the proper component.

The paths and solder points need to be redone, and that's about it.
Changing the component in question is a quick fix as soon as I find the replacement. All the preparations are done as in removing the patty material and fixing the paths.
So the math is simple, $150- 200 + for a used ECU ($400+ for a new one ) vs a new transistor and soldering on my spare time.