Check engine light problem

It sounds like your car is going into diagnostic mode. We take a paperclip at the obd1 connector and short 2 terminals which allows us to get the comp into diagnostic mode.

Somewhere, there is something shorting out the Sig RTN on the main terminal and the STI terminal. Where, I don't know. But start at the connectors at the rear of the curb side strut tower, and go from there.
Scott