VREF voltage too high

I'm banging my head here over a vref hihgh voltage problem on my 1990 GT....I'm running an EPEC and have two spare 89-93 EEC's here and no matter which one I hook up, I get a reading of 12+ volts from the vref 26 pin (instead of the normal 5v) after turning the key forward....what could it be? When using the epec, I get the 5 volts, key off...then turn the key forward and I get 12+v....on the A9L, I get nothing, key off...turn the key forward and I get 12+v....At first I thought this was the signal return wire but I think I've further traced it to the #26 vref...Even if I unplug all the sensors, I still get this 12+ from vref....with all sensors plugged in, the datalogger shows 100% TPS, -40f ACT, -40f ECT, and so on.....This problem has been around this car since the last owner had it and I thought it might be easy to fix....the car was originally an AOD car that was swapped to a t5....I checked all the clutch switches and nuetral safety as well as plugs on the tranny....nothing....I just worked many hours fabricating a turbo setup for this car and I would very much like to get these sensors to producing proper feedback so I can drive this thing....what could this be? TIA

Thanks very much....I'll try those tests this evening....

Mine starts easily when cold then floods out while cranking with a hot engine...I think I've found my problem, but not 100 percent sure....o2 sensor harness....there's a dead end wire (pin30) in my 8pin socket by the MAF...someone at another forum pointned that out as a possibility....the male part of that plug has 8 wires going in and the female portion has only 7.....I think I need to check another stang like mine to see what mods I need to do to my o2 harness then take it from there.....

pro50, did you convert from auto to T-5 or vice versa? if so, here's a link to a similar problem as mine...

Fixed it!!! My o2 sensor harness was in fact for an AOD car....I took apart the 8pin connector, swapped pins and the car runs awesome now (with another ecm)....having the wrong o2 harness will fry any ecm you connect to it, from what I understand... I guess you learn something new everyday....