I got my alternator replaced at a shop and when I went to pick it up end of day, they told me there was brake fluid falling onto the PCM and it had a surge. There was indeed some sort of dark residue on the PCM, and another mechanic told me I need to replace the master cylinder, but I am skeptical that the master cylinder is the issue as my brake pressure has been fine. I'm going to check the brake fluid system myself and see what I can find, but has anyone had an issue with something leaking onto the PCM before? Does this sound right
​right?

Also, is there something I can use to cover the PCM in the meantime so it doesn't sustain further damage?

 

Anything. Duct tape a baggie over it. Then use an aerosol brake cleaner on the MC to make sure you see where it might be leaking.

I'd be curious as to any codes it may be throwing. Have you had an OBD reader on it yet?

 

The check engine went off once I replaced the alternator and it hasn't come up since, so I hadn't checked the codes again.

 

The alternator may have triggered it then. You should check for any stored codes. If there aren't any, the PCM may be fine.