Got an 87 tbi factory gauge setup and have a 411 PCM truck harness, I have the MIL wire pulled out of the truck harness near the computer. Does this put out a 12V+ signal or supply a ground for the light to come on. Any way that would hook into the service engine soon light in the stock cluster? I "thought" the tbi computer supplied a ground to that light bulb to turn the light on, maybe I'm wrong in reading these old wiring diagrams. How did everyone hook it up?

 

did some poking around, looks like I just hook the wires up and the light should function as normal. Guess I'll put the key in the ignition position and start grounding the factory wires near the computer hook up and see which one lights up the light. From my research it looks like brown, tan/white, brown/white or something similar on this full size truck harness

 

R46 (BRN/WHT) to C207 pin C (BRN/WHT for EFI cars, WHT/GRN carb cars)
Same pin, all years, birds and camaros

PCM grounds the MIL light to turn it on

 

its a 87 suburban tbi chassis harness. I'm assuming the wiring color would be the same as a thirdgen of the same year, knowing how GM uses similar connectors throughout the division. Rained all night, I'll look tomorrow after work for that color.

 

Same function on all GM cars. Just a matter of tracking that wire down

 

brown wire with white tracer did it, thanks again