95 SHO MTX - Scan Tool Problem

I have a 95 Ford SHO MTX - engine is 3.0 DOHC, Mileage is 125K. I hooked up a Actron 9110 Scan Tool using the Ford OBD1 cartridge and OBD1 cable connector supplied with the tool to the engine compartment connector ( 6 prong (black) + 1 pigtail (gray)). The Scan Tool ran though the KOEO program fine. When I changed to run the KOER codes the engine would not restart - it finally did and died shortly after, during the restart the tachometer was not working. Is it possible the Scan Tool shorted out something in the computer? What are the next steps to try to diagnose the problem? I read in an SHO forum after the incident that the pigtail lead for the Scan tool should not have been connected to the grey pigtail on the engine harness? Was this the problem - and the tach has now been shorted out? Thanks.