Ex850R;14022 wroteA cheap eBay $30 delivered bright orange obd code reader does the job well , can clear codes and shows impending codes
Correct me if I'm wrong, but last time I looked into it a cheapo code reader only does generic codes, i.e. engine & perhaps transmission codes. It doesn't do ABS, airbag, cruise control or power seat codes which are Volvo specific. And you can't use the onboard diagnostic system in component testing mode or calibration mode (calibration mode is essential if you've replaced parts on power seat with memory feature), you could do all that on Motronic 1.8 or LH-Jetronic 2.4 by just using the diagnostic box in the engine bay.
If there's a code reader that does all that for under $100 I'll buy one straight away.