2000 C70 OBD2 codes p1550; p1620; p1623

[Lochaberlaird]

Hi All, I have just bought my very first Volvo and by the time i got it home the check engine light was on so i got out my trusty code reader and got three codes p1550; p1620; and p1623.
having looked through the forums it seem that the p1550 code is abs related (although no abs light on) and it also appears the abs module has a common fault so could someone link me the post that describes the repair procedure for it or how to identify if a faulty one is fitted.

I have also found that the p1620 code is cooling fan low speed sensor but can't find anything as to how to confirm/repair that. and lastly the p1623 code i can't find anything as to what it may be so if somebody could help me with those as well i would really appreciate it.

thx to anyone that can help