Missing the \"Service Engine Soon\" light. Anybody have this happen to them and what was the fix? I first noticed that I did not have the Service Engine Soon light when I went to check for trouble codes. I was checking for codes because my 1989 K5 350TBI kept stumbling and cutting out- anytime I gave it more than 1/4 throttle. Damn thing idles fine and has power, just wont take more than a partial throttle. I found a set of GMC shop manuals for model year 1987. They appear to be close enough to work off of. My Haynes manual is about worthless. I have found that the bulb is good, the power to the bulb is there and the wiring to the ECM is OK. This points to a defective ECM. I will be swapping in another ECM to see if this is the fix. I will be shocked to know that the ECM can still run- but in a degredated state. I'll post back after the swap. If I do need a new one, fortunately Auto Zone and Advanced have the ECM in stock for $71...but with a $95 core charge.