ktg

My 2004 GMC 2500 with 6.0 suddenly started running rough several weeks ago but there have been no codes. It starts perfectly and seems to run a little better when it's cold. When hot, it idles like a dragster. When accelerating, it suddenly will start running fine around 2500 rpm and then back to rough when it shifts to a lower rpm. Going slightly uphill around 45 mph with cruise on, it shakes pretty bad. Mechanic said there's nothing he can do with no codes. Fuel trims are close to zero at idle and jump to 8-10% under load. I thought I found the problem on scan tool. It said it was calling for 117 on IAC but position was at 1 and didn't move. I then realized that it doesn't have an IAC. Installed new plugs and wires about 2 weeks before this started. Anyone have advice?

I think after 7 flippin' years of fighting this problem every winter, I've finally fixed it. I began to suspect that the starter may have problems earlier this year. My battery drain was getting really bad, even in warmer weather. I had to attach a battery tender every night to keep my 2 yellow top optimas from going dead. I changed the starter several months ago and haven't had a problem since. Even in freezing weather now it starts like new. Hopefully when we go to -15 degrees, it stays starting like new.

Update: My battery drain only seems to occur when the temperatures are cold, like below freezing. I've battled this for many years now without finding the exact problem, just that if any of the 3 BCM fuses are installed, the drain is WAY more than it should be. I decided to treat the symptoms since I can't find the problem and install dual yellow top optima batteries. I tried to get 2 Sears Platinum batteries as they seemed like a better deal but our local sears store doesn't carry batteries and I didn't want to chance a warranty problem being 180 miles from the stocking Sears store. I only got the job half done a couple Saturdays ago so I only had one of the optimas hooked up. It was dead a couple days later. Last Saturday I got the install completed and ran the truck for a while to charge the batteries. It sat untouched till today (7 days) in weather ranging from -5 to 25 degrees F. It fired right up without even seeming weak. I guess I've treated the symptons sufficiently but I still wonder what the problem is.

I took my truck to the dealer and had them check it out when they were also fixing an ABS problem. They said they monitored the parasitic drain for an hour and it was within specs, less than 40mA, but I don't remember exactly what, then they charged me an extra $60 for checking it. I took it home, let it sit for 3 hours and then checked the drain. It was about 3.5A still. I checked it several times since and it's never been lower than about 2.5A and only that low after it sits for a much longer time. i don't know what thier fancy machine was checking but they should have used a simple meter. I took the truck back to the dealer and had them reflash the BCM. That was a waste of another $140. It's still doing the same thing. The letter from GM that I found for 2003 trucks mentioned something about the BCM needed reprogrammed because it wasn't reading the steering wheel position correctly. The only thing I can think of is a bad BCM or steering wheel position sensor. There are no error codes to give me a clue. Anyone have any other ideas?

My 2004 GMC quadrasteer has developed a parasitic battery drain that kills the battery if it sits for more than a day. I've traced it to the BCM. I checked the drain with a meter after the truck had sit for 4 hours. The drain was about 3.5 amps. The drain after sitting for 12 hours was about 2.5 amps. If I pull all 4 of the TBC fuses then the drain drops to about 20mA. If I put in any one of the 4 TBC fuses the drain jumps back up. I notice there's a service bulletin for 2003 trucks about reflashing the BCM to fix the same problem. Might this apply to my 2004 also or am I going to have to find a new BCM? Anyone have experience with something like this?