Since the Emissions light had been on for a bit I decided to see which, if any, problem codes had been caught. I got a clean bill of health all the way through. Nothing but elevens. The last time the light was on, all that was needed to cancel it was a simple reset. My neighbor, a mechanic at Ford, told me that the light will come after a time frame to suggest the vehicle should be taken for service. The truck had a clean bill of health then as well.

My neighbor explained to me how to reset the light. It involved a pick (or paper clip) poked through a papered over hole in a small cube hung under the dash near the headlamp and wiper switches. As I recall it was tricky as you had to poke while the key was on (or off then turned on, or some other sequence). It had to be at least 18 years ago that I did this. I need help remembering the process.

Anyone?

 

I've seen it called an 'inferred mileage sensor' or 'extended useful life' sensor.
Mine ('87) is more under the center of the dash.
Poke something in the hole and cycle the key on.
Hold the pin in for 5 seconds.
The emissions light should go out for the next 60k miles.

 

I'll do it. And the truck has just turned over 122,000 miles. ON A 1986 MODEL!

 

Found this thread in the "stickies" at the top of the page for the 1980-1986 forum: https://www.ford-trucks.com/forums/1...ons-light.html