Codes P0605 & P1550

I have a 1999 Jetta III, TDI. I am getting the following codes, P0605 (ROM error and P1550 Idle speed aux. mal fun. I do not know what to check next or how to fix it troubleshooting charts for those DTC codes could help you troubleshoot it, if that’s what you want. Some public libraries have a subscription to, or, you could buy an online subscription for $15.