If you have a key type ignition, you can only retrieve error codes that are 'active', or while they are occuring,(hold the light switch for a few seconds to show the codes) otherwise you'll need the dealer's hook-up. I believe the keyless ignition has the ability to retrieve the codes after the fact, the operators manual should tell how to. Also in the operators manual should be a list of codes and what they mean.What machine?
For newer machines, I thought you held the light button for 4 seconds? and it will flash the error codes. I may be wrong, its been a while since i needed to do this.