Engine light

I have a 2005 1500 with 30, miles on it. Whenever the temperature goes below 20 degrees the engine light comes on and stays on until the temperature is over 20 for over three hours. What could the problem be? (4.7 lt engine)

Did you test your coolant?

Let me see if I understand.

You start the truck in sub 20F temps. The Check Engine Light (CEL) comes on. It will stay on forever until the ambient temp is @ greater than 20F for three hours. If the ambient temp remains below 20F …let’s say for days, the CEL is on all of that time regardless of if you’re driving 15 minutes or 24 hours in a row.

Is that correct?

Well (LOL!) you have to factor the data and isolate the conditions. You gave a number of conditions for the problem to exist. I merely verified that you really meant what you said.

What you probably meant is when you start below 20F you get a CEL light. If it’s above 20F but WAS below 20F overnight …then after 3 hours of above 20F ambient temps …you don’t get the CEL.

If this is what you meant (it wasn’t what you said), let’s see if we can factor it further.

How long are your driving events in either case?

What’s the code? Beefy, you’ve been here long enough to know to get the code. With that, maybe we can make a better guess what doesn’t like sub 20 temps.