Yeah, I was right, you don’t need a scanner.
http://groups.google.com/group/alt.autos.volvo/browse_thread/thread/efc1468456b6410c/564566c411483512?lnk=st&q=1993+volvo+850+codes&rnum=1&hl=en#564566c411483512
And here are the various code for block A2, the engine.
http://www.volvospeed.com/dtc_a2_codes.php
http://www.volvospeed.com/maintence.htm