Don't think you need a code reader. As far as I know, the '92 240 models had OBDI which can be read from under the hood of your Volvo. Look at the driver's side strut tower, there should be one or two black boxes that are about 1.5 x 2.5", there will be a cover over each. Pull the cover off, you'll find six holes under each and what looks like a jumper/probe sitting on the outside of these modules.

Check out the 700/900 FAQ in the Features menu above, most, if not all of the OBD diagnostic info will pertain to your car. The Bentley repair manual, specific for 240 series cars from 1983 to 1993, had the codes and procedures as well. If you are a DIY mechanic, this manual is worth every penny.

Good luck,
Bean
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'80 242GT 93k, '94 945T 139k, '89 765T 68k (new '94 B230FT)