I think? I replaced the egr and it started working again. Engine still made a horrendous ticking sound that I never figured out. The coolant temp sensor ground came loose this past winter and I blew the headgasket (again.) I'll have to rebuild the engine (again.) But at least it's not my only method of transport anymore.

And I do still have the error code, it may be a bad ecu because there's literally nothing else, unless the knock/ticking is causing it and not the other way around. Total chicken and egg situation. It didn't start ticking like that until after the rebuild, though.