So after finally fixing my secondary air system code (it was the valve), the SES lights up again.
It was the DMTL pump system, switching current too high, I think?
Reading
this overview was a big help in understanding the system, now I'm looking for practical troubleshooting advice.
First thing I did was swap out the gas tank cap with an E46 with no codes. It came back after 2 days, wasnt that.