Those wires are not part of the engine wiring loom. I replaced mine by opening the connector and soldering new wires in (there's only 3 IIRC). I suspect it's cheap enough to buy the small loom from a dealer if you don't feel up to it.
You may find that the main engine loom has already been replaced which is why you don't have any error codes. Check before committing to replace the entire loom.