SDHNTR

I have an 06 5.9 and for the first time my CEL came on right at start up yesterday. I immediately thought of the gas cap and when I got out and checked it, it was definitely quite loose. Of course, I tightened it up, but the CEL still has not gone off. I have cycled the key through starts at least 10+ times and it is still on. Disconnected both batteries for several minutes and still on.

Is this normal? Does it take that long to reset? Or do I likely have some other actual problem other than the loose cap?

AH64ID

I don't think the Cummins ECM monitors the fuel cap.

Have you done the 3 key trick to read the code?

key on-off-on-off-on, code should appear on the dash.

rockcrawler304

Here is the link for the "How To"

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

SDHNTR

Just did the key thing, exactly like on the video. Got nothing. No code and it doesn't say "done". What now?

cbrahs

even if it was a gas cap related light (ah64 is correct, the diesels don't monitor evap system as we don't have an evap systyem) it would take 3-5 start cycles to self clear the code (1 start cycle is starting the engine cold, running until operating temp and shutting it off allowing to get cold again)

if you disconnected batteries and light is still on, it means it is a hard failure. need to swing by autozone and ask them to pull codes and post what codes you are getting and we can help ya out from there.

SDHNTR

Are you sure? My Dad has an 04 and he said his CEL has come on when his cap was loose. Seems I've heard of it on forums before too.

It just makes sense as this is the first time I've ever had the light come on and the cap was definitely loose. The reason why it was loose is because I was trying to stick a siphon hose down there to pull out a little fuel to start a campfire. I know, dumb. Kind of a big coincidence for the light to just randomly come on for some other reason right at this time.

I unfortunately don't have an autozone nearby. Might have to bite it and take it by the dealer.

AH64ID

There is nothing on these trucks that will do that.

15 Digger

Happened to me a few times. reset cap and it took a few days of driving cycles but always worked.

cbrahs

our diesels are not equipped with an evaporative emissions system. it will not set a code for a gas cap (small leak detected or large leak detected). not capable never will never has.

15 Digger

Why would i have a light that went away after resetting the cap each time, otherwise never any light or problems? Just asking to learn of other reasons.

AH64ID

Just lucky.. its not related at all.

SDHNTR

Yeah, this is confusing. Do a search here and you will find a number of people who say they had the light come on after a loose cap, then a number of people who will say the trucks don't thow a light for that. Not sure what to think.

My plan is to just give it another couple days as I have only had 2 complete warm up and cool down cycles, and see if it goes off on it's own. If it does, I plan to just drive it like normal. If not, I'll take it in. Anyone see any problem with that?

AH64ID

Personally it would drive me nuts not knowing what the CEL was for.

SDHNTR

I just drove the truck. Started it for the 3rd warm up cycle since the light came on. CEL went off.

I hear what you guys are saying, but it sure as heck seems like the loose cap was my problem.

AH64ID

You'll never know if you don't get it scanned. The code should still be stored, so next time your by an auto parts store get it scanned.