Ok thanks for the input; but any code from the multitude of the possibilites would set the light to come on in his case, suggesting a code out as it impacted your truck is more or less speculation and leads to incorrect diagnostics and possibly wrong $$$ spent to correct the problem, been my experience to drill down with vehicle specific information as much as possible.

---AutoMerged DoublePost---

For the CPS issue it could also be the harness with intermmitent

---AutoMerged DoublePost---

Danged auto merge feature this site also more important this site specifically to have independent post on ones own vehicle as it is hard to comment to an individual post without the auto merge confusing the discussion,

Admins automerge is done why??????

 

Will a check engine warning light ever be a gas cap malfunction---like what happens on gas engines? I own a 2008 GMC Acadia which was recently diagnosed as such. Now I have two vehicles....on one diesel and gas with the same symptom. DK

 

No a 6.5TD will never set a gas cap malfunction code.

A malfunctioning fuel cap will however cause fuel starvation in some instances.