Volvo: 1999 V70 XC Cross Country, synthetic transmission fluid, engine faults

Question
How do you reset the check engine with out visiting the dealer, the car runs fine. The passenger dash airbag light goes on stay's on then goes off,again with out going to the dealer what can I do. Is there a inexpensive hand held engine computer reader ? The car has 116,000 miles engine sounds good, I plan on changing the synthetic transmission fluid any tips other than flushing it out as well. I like the car but there are issues with them,lastly keep it or sell it ???

Answer
Gus,
There is no way to reset fault codes without a scan tool. Volvo one is the best called VIDA. However I have heard never tried, to disconnect the battery overnight.
There are scan tools to buy. Some will only read and reset engine faults nothing else. SRS lights and others will need the upgraded scanners. The best ones will read the manufactures codes not generic ones. Yes flushing and using syntheic oil is not a bad idea. Have the flush done at a shop that uses the flushing machines is best. That exchanges all the fluid. If you like the car and don't mind it's problems keep it, although it maybe time to trade. I would trade.