This has been common after a spark plug change cause of the gapping in the plugs. The wrong gap will cause random misfires. Try checking the gap on ur plugs. And even if they come pre-gapped, always check it anyways. If it were a bad coil you would feel a misfire. The intake gaskets can cause this but you would also get a lean condition.

 

The plugs were changed about 60k miles ago. The problem just started showing up about 5000 miles ago. It is possible that the plugs could need another change. It could also be that the plugs were not changed as I was told. We bought the truck from the dealer used and was told the plugs were changed.
Thanks for the information. That does start to narrow it down a bit.
john

 

I have thee 01 2500hd 6.0. I have the same issue as johnstance. did you figure out what it was? I have new plugs and wires, fuel filter, air filter, pcv, fuel metering valve, cam position sensor. the ses illuminates at about 50-60mph and 2400rpm and above. The light will also come on in park at about 2400 rpm. I can put my foot into it and accelerate from a stop to 50mph getting above 3000rpm no light. any ideas?

 

i have not done much to resolve this since posting. i was going to do the things you listed but it would seem that it would be a waste of time considering that you still have the same issue.
One development is that every now and then it does idle a bit rough cold. My next step was to have the O2 sensors checked out. it may be that if these are not working correctly that the air/fuel mixture would be incorrect at high rpm and cause a slight misfire randomly. This would also explain a rough idle if the mixture was a little rich.
The issue does not seems to affect mileage or performance so it is a ways down the to-do list. i was going to have my mechanic check the sensors this month sometime. i will be sure to report back now that I know I am not the only one with the issue. Mine behaves in the exact same way. I have not been able to cause the misfire in park however but i have not really tried. it seems to happen more when the engine is not under load (going down hill or decelerating on the highway).

 

After I installed the cam sensor I went to the shop and had them use the scanner to relearn the cam. Seems to be working for now. I am taking the truck on a 600 mile trip this weekend so i'll let you know if that actually fixed it or it just hasn't built up enough misfires to illuminate the ses yet. BTW, my 01 has 125k miles and had a leaky transfer case. You might want to look up the thread on leaking transfer cases. I used jb weld and the case has been dry for a while. May do the real fix later. good luck.

 

Ok Guys. My story is slightly different. My "light" has been going on and off since the weather has cooled off in AZ but the truck runs very rough for the first 10-15 miles then smooths out. It's even cut off at a stop light once or twice. I just did an oil change at Wally World (only because I trust this particular location) before a 300+ mile trip to Vegas and the tech cleaned out my air filter and the light cycled off about 20+ miles after that. The "light" was off the whole way to Vegas then went on the next day and has been on for the last 3 days. Up until yesterday it was always just a solid "CHECK ENGINE" light but this morning, which was a lil chillier than the last couple of weeks, it started flashing when I started it up then went solid after about 5 minutes. Times are hard and I have a good mechanic but he's not cheap. I think I need to check plugs and wires but dont know the best way to do that AND if it is the plugs and wires should I go dealer parts or local Napa? If any of you guys have used Auto Zone let me know because I dont have the greatest confidence in their parts. I'd rather spend my hard earned money on quality parts and do the labor myself. Any input you guys can offer would be great.

Pops

 

Well, since my last post there has been no reoccurrence of the flashing ses. I love my 01 2500hd. Only question I have is... What kind of mileage do these things usually get? I seem to be getting between 10 and 12 mpg. Good luck.

 

Sounds like the cam pos. sensor was the trick. Did you do it yourself fat tire? If so, is it a tough job?

I have been tracking the mileage for our truck and the average is right around 11 MPG with no load or towing city and highway mix. So you are seeing what we are. We pull a 29' travel trailer and get closer to 7 or 8 doing that.

 

The random misfire has been ongoing for the past year. I had to twice replace one of my catalytic converters because of the misfires. It tears the converters apart. I have continued to get the vehicle checked out and I think I have narrowed the issue down to two possibilities. There is excessive build up within the cylinder walls, that I have been told could result in a reboring of my cylinders. I have also been told it could be that the injectors are corroded. Anyway, about two months ago I put in some SeaFoam in my gas tank. A month ago I put in some Fuel Injector cleaner with Techron. And to try and clean out the cylinder walls I put some SeaFoam in the main engine compartment. Then about a week later I got an oil change using a high mileage oil. So far no code 300 and my truck is running a bit smoother. We will see how it goes. In the mean time I now have a small oil leak in the rear main and the gasket in my oil pan needs to be replace. It is dumping a more oil than I like to see. I have also noticed that my air sensor is on the fritz. Got to love Chevy. Can't wait to buy my next one.

 

It appears the cam sensor was the problem...or at least the last straw with mine. Not too hard to replace. Its between the back of the engine and the firewall. It took me a while because my hands are no longer the size of a 5year olds. After replacing it I took it to the shop and they took 5minutes to hook up the computer for the relearning process. No light since then.