Out of curiousity, which scan tool do you have? The Bosch Hammer, JDS Spanner and the Durametric's units all use the round 19 pin AMP socket located under the dash/blovebox on the passenger side by the carpeted kick panel. It has a screw on cover on it, but its easy enough to find once you look under the dash.
This is true. But the DME will store error codes aven the the CEL light never tripped.
Example being:
Pete had the hammer on my car, he was able to tell me my airbag had been disconnected for 82 hours. (I had a MOMO steering wheel as as a CS wheel so the airbag had been removed)