[clinebarger]

Originally Posted by kristian_dancer

Ihave been haveing exactly the same problem,

I have an 86 c20 dually converstion. Check enginelight would come on on when I went over 55 then off every time i turned ignition off.
Now it stays on.
I have no plug for code reading under dash.
No obvious smog equipment under the hood.
Trucks runs fine other than needing a break seal replacement on the dually rear end.
All I want to know is that im not killingthe truck and that the check engine light is not coming on for a good reason like trans temp or oil pump failure etc.

Did you see post #29? Do you have the "smog pump control module" on the firewall?