How do you test an ABS module on a Volvo S80? Getting P1633 and P1631 codes.

Hello, There is a high likelihood that your ABS module is bad. Much like thousands of other Volvo of that era. It is a very common complaint, but you are correct, it needs to be tested. The best and most reliable method: diagnostic scanning with professional grade tooling and software. That will allow the technician to quickly and easily diagnose the issue. By now, there may be a tell-tale that the Volvo techs know to diagnose it without the hassle.