failed MD emissions test. Looking for reasons why and how to inexpensively fix.

If the check engine light doesn't come on key on engine off, then it likely doesn't work and alert you to the fact that there is a problem when one occurs. We find everything from the bulbs being removed, to caps on the LEDS, to wires being cut between the instrument cluster and the PCM. You need a schematic to see how the lamp works and start your troubleshooting. A fully functional scan tool like the IDS (formerly shared by Mazda and Ford) will have the ability to try and command the lamp on and off and save some time with the diagnostics.

scan codes and post so we can adv

That means Key On Engine Off, (KOEO). Were you there when he scanned your trouble codes and do you remember if he started your engine? Most of the time it's as simple as that when I'm asked about the same KOEO code. Good luck!