hackengineering

I have an 87 4runner with auto and 22re. I have been attempting to get this 4runner up to running condition and so far everything has started to work pretty well. I have put a few hundred miles on it and noticed each time i get to a cruising speed and do not move the throttle for about 30 seconds the CEL comes on. If i let off the accelerator and then get back on it the light goes off.
Given this light goes off each time i let off the accelerator is there a stored code i can find. Anyone have any thoughts as to what this might be. Nothing has really been done to this rig but there are alot of wireing grimlins that i have been working on.
Thanks for the advice.