I have had my truck in for the third time for the 900 to 1300 rpm surge and buck problem (my04.5LLY) The dealer reflashed it the first time and the again the second time. Now they tell me it has the latest updates but the problem is still there. Says GM is aware and will notify me when they have a fix. I am making an appointment with a different dealer to see if someone else has any better luck.

The service MGR said to me its not that noticable, I replied that driving the truck by itself its not that noticable, but hook on my 10K plus fifthwheel and it feels like it is going to break somthing.

How many of you have experiened this problem and the reflash did not cure it?

I also had them install the dampeners on the exhaust for the drone noise and that didn't help it either.

My 2005 does it also. It is annoying,but manageable. Hopefully they will fix it.

This morning my truck bogged down when shifting between 2nd and 3rd gear, then it would not shift until I came to a stop, after a couple of trys it worked fine right to the dealership. service tech says he test drove it and had no problems, no codes (go figure !!) I'll pick it up this afternoon

My 2004.5 has the same problem. It's been reflashed twice, most recently in mid Feb, with only temporary improvement. In fact, the problem is gradually getting worse and is most noticable when our 13k 5th wheel is in tow.

I'm going to take it back in again this week and see what they can do.

my 04.5 lly didt do it until i started reading these posts. usually after 12 noon and have been towing all morning. at idle it feels like rpm go down just barely then jumps 100 or so rpm. only while idling at stop light or when idling in neutral while loading or unloading trailer. Also the tone in exhaust changes often while idling, like the turbo vanes are changing pitch. I have had truck for 1 year now with 61000 miles and have never been to dealer for anything, no reflash or anything. other than that truck is a kick arse, bad arse mother trucker.

My 2004 Sierra was to the dealer a couple of weeks ago. I had idle surge and it smoked alot while it was idling. The dealer said it was a bad injector and that they would order it. They also stated that they reprogrammed the computer to eliminate the problem for now. Well it has been running okay since then and I have seen an improvement in the mileage. I still haven't heard back from the dealer on the injector replacement but for now it's running okay.

Bill

Mine will surge bad on a cold idle. Had it flashed yesterday for the first time and this morning idle was smooth. Also the engine is much smoother and the 2000-2500 rattle is all most gone. I hope it all stays that way.

Greg