CEL oddity

[cmc76]

ill say this first, i have NOT yet put a scanner on. It will be a few days before i can.
CEL light had been going on, seemed like it was tied to when the temp dropped below say 25. But on 2 occasions, even when chilly out. I fill up on gas and tighten the cap, the light goes off. Ive done some searching and I think what I am reading is that the gasket on the cap can cause?
This morning, i let the truck warm up for about 5 minutes before leaving, and in that time the CEL flashed for maybe 30 seconds, then stopped.
I havent noticed any other symptoms. Fuel milage is good ( as good as it can be ). Idle , acceleration, everything else seems normal, even when the light was on.
Ideas would be helpful. And i do plan on scanning for codes, my mechanic at work is tied up.

 

[SLCHOE]

ill say this first, i have NOT yet put a scanner on. It will be a few days before i can.
CEL light had been going on, seemed like it was tied to when the temp dropped below say 25. But on 2 occasions, even when chilly out. I fill up on gas and tighten the cap, the light goes off. Ive done some searching and I think what I am reading is that the gasket on the cap can cause?
This morning, i let the truck warm up for about 5 minutes before leaving, and in that time the CEL flashed for maybe 30 seconds, then stopped.
I havent noticed any other symptoms. Fuel milage is good ( as good as it can be ). Idle , acceleration, everything else seems normal, even when the light was on.
Ideas would be helpful. And i do plan on scanning for codes, my mechanic at work is tied up.

Too much guessing. The CEL illuminates because there is a current code. If for some reason the problem that triggered the code falls back into parameters, the light may go back off (depending on the code) such as an intermittent misfire.

A flashing CEL however indicates issues that can cause detrimental damage to emissions control devices. This is most likely a multiple misfire issue. Misfire's can kill your catalytic converters FAST and that is why it's flashing. It basically means shut the engine off and fix it.

First step. Pull the codes.