I am working with an 87 firebird formula 305 M5 tranny. I have removed the q-Jet and swapped to an edlebrock 600CFM performer with manual secondaries. also added a new MSd streetfire HEI distributor vacuume advance. I have pulled the ignition source and (instrument) tach wire from the two connection plug that went to the stock ignition coil. The car runs and my tach works...great.

Ive read in a few places that the ECU gets its tach signal elseware. Now i realize that the ECU is not needed at this point but it is still in the car and my check engine light is on because of the mass of connectors that are unplugged i would assume. Since its OBD I i went out on a hunch that the only reason that the light is on is because it has not tach trigger and sees no load for ignition maybe? I tried running my tach trigger into the "white" wire on the 4 pin connector that connected to the OEM distrubtor. With the car running the check engine light sort of flashes with out a real pattern and the shift light sometimes flashes down low.

Is there a way to provide the ECU with a tach source? will it get rid of my check engine light? Will my shift light work? I dont really need the shift light to work but it would be nice to get rid of the check engine light short of unscrewing the bulb or snipping a wire going to it.

Thanks for any help!