Have a 2004 3rd gen 5.9L, the yellow eng light (the one that is in the shape of a eng) has come on, from the book it is a problem with emission control. Checked the gas cap what else might I look for? How would I reset the warning light once fixed or would the truck comp do that on its own?

 

What are the codes?

https://www.dieseltruckresource.com/...s-t224833.html

Sometimes you have to turn the key 4 times vice three...

 

madhat:
Thanks I got the code after doing your trick. Now I hope you can tell me what it is for P0071 is what came up

 

0071 = air temp rational.

I get that in spring /fall. Open the garage door and when starting the truck the cold air is noticed by the intake sensor. After a few days of normal starts it will go away.

 

Cold Air....what the heck is that??? Just read this and got a good laugh as we have had nothing but 100+ degree days for 43 days in a row where I live here in Texas....with NO RAIN EITHER!!!! I'd give my left.....uh....over-day-old-sandwich for some even remotely cool air . Just had add my .02

Hope you get your problem fixed and that it's nothing major.

 

I got that once after washing my truck with the power washer. Somehow the ambient temp sensor didn't like getting wet. I unplugged it and let it dry, plugged it back in, reset the MIL, and it never came back.

The computer seems to check that sensor reading against the intake temp sensor to verify they are both working.