I have a 2005 Chevy 2500HD, 4x4, crew cab, with a 6.0L engine. Almost since I have owned it, the truck has produced a sound similar to spark knock when traveling down the road at 1500 – 2000 RPM. The ticking or knocking sound normally can be heard when traveling at constant speed and the accelerator is lightly pushed. The noise does not happen all the time, it does happen most days. Colder weather seems to make the noise easier to produce, but it can be heard often on hot days as well.

I have taken the truck back to the dealer several times for the problem and they say it cannot be spark knock since the truck has sensors to detect and prevent that. One person suggested having the dealer check the exhaust system for broken welds. I asked the dealer to check for that, but they said the exhaust system also could not cause this problem.

Anyone have a similar problem or know what causes this?

 

if it has no codes,its probably due to crummy gas...

 

Bad gas was my first thought, but I used gas from many different stations (both brands & locations) including 91 octane, none made any difference. The noise may not actually be spark knock, but reacts in a similar way and sounds very much the same.

 

I know off hand that the timing table for 1K to 2K is pretty "tame" and doesn't accomodate cold weather as well as warm weather. I have heard slight knocking in the cold weather on mine too. Any mods to your truck?

 

No modifications to the truck that I know of, and it was purchased new from the dealer. They also say no codes were found during service. The ticking / knocking can be pretty annoying sometimes, especially then passengers ask what’s wrong with the truck as you are cruising down the road.
The dealer service personnel say that the newer 6.0L’s will not knock since the computer will adjust for weather and other driving conditions. I am not sure that is true or they are just not wanting to deal with the issue.

 

true

 

Either that or its might be something fairly simple. Has it always done this? Mine comes at cold temps until the engine reaches the full 195 degrees and then it stops. Yours sounds more perminent. Maybe a knock sensor went bad? I don't know if it would go bad without throwing codes but it could be the reason why the computer won 't adjust the timing to correct the knock. But it could be a run-around deal with the dealership too. Whens the last time the pcm was flashed?