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We traded our 1997 1500 Suburban for a 2003 GMC Sierra 2500HD, Duramax Crew Cab (Demo w/ 5000 mi) to cover our TT GVWR of 6900lbs. Our Suburban was at the max tow capacity and even over at the TT GVWR. Our first trip was a disaster as the Sierra towed worse then our Suburban. We maxed out at about 50-55 mph on a level straight away and could get no more power out it! On inclines, it was even worse.
We took it to the dealer where they replaced a sensor and reprogrammed a computer (TCCM?). On the next trip, nothing had changed and the performance was a bad as before. Talk about disappointment!

We feel the dealer will hopefully find and correct what ever deficiency there is with the Sierra.
Anyone know anything about this from past experience?
 

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nikki girl said:
<FONT face="arial,helvetica,sans serif" size=2>We traded our 1997 1500 Suburban for a 2003 GMC Sierra 2500HD, Duramax Crew Cab (Demo w/ 5000 mi) to cover our TT GVWR of 6900lbs. Our Suburban was at the max tow capacity and even over at the TT GVWR. Our first trip was a disaster as the Sierra towed worse then our Suburban. We maxed out at about 50-55 mph on a level straight away and could get no more power out it! On inclines, it was even worse.</font><FONT face="arial,helvetica,sans serif" size=2>
We took it to the dealer where they replaced a sensor and reprogrammed a computer (TCCM?). On the next trip, nothing had changed and the performance was a bad as before. Talk about disappointment!

We feel the dealer will hopefully find and correct what ever deficiency there is with the Sierra.
Anyone know anything about this from past experience?

</font>
How many miles ??

Mac
 

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Definately a problem there somewhere Tom. I could tow my 8,000# high profile FW into a 30 mph headwind at 80 mph if I wanted to. Put a post down in dmaxalliTech's area. Could be something as simple as that variable resistor (potentiometer like) that the "go" peddle is attached to. I seem to recall someone with a similar problem and he just wasn't getting 100% travel out of that pot.


Hey, here's a quick test. See if you can reset the "Remaining oil life" back to max using the procedures in the Owners manual. Turn key to on, go to "Remaining Oil Life", and press the pedal all the way down three times. If it doesn't reset, you're not getting full travel out of it.
 

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Im interested in the number of miles too.

It seems anyone that tries serious towing prior to 5000 or so miles has trouble, but once they reach near 10k or so a new truck shows up. I think its a software/break in issue.
 

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Discussion Starter #5
Thanks everyone. There was never any towing done prior to 5000 mi. It now has around 6200.


I'll try the test suggested by gwmayes and see what happens. I have it going back into the dealer Monday and I'll bring this to their attention. Let's see what happens after the second visit. Will post results.
 

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Its a long shot but it sounds like fuel starvation. This could be clogged filter or turbine runnong slow. I had a similar problem on a gas job and it turned out a baffle broke loose in the muffler and partially plugged the exhaust thus restricting the engine from sucking enough air.
 

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Hopefully its something simple.

I had a 99 Suburban I traded in on the truck and it was obvious my truck had gobs more power right off the bat.
 

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While spending a couple of weeks this summer at a campground in South Dakota, I talked with a fellow driving an '03 2500 (as I recall just over 6,000 miles on it) who expressed the same concerns. We took the Juice unit off of my truck and put it in his .... he couldn't believe the difference. He got so excited about it that he actually buttoned up his 5er and pulled it several miles as a test.
The fact that his truck responded as it did to a shot of Juice made me to believe he had programming, rather than mechanical, issues. I know he was going to take it back to his dealership to have then check it out but have no way of knowing what the final outcome was. Nikki Girl, if your truck is stock and you can find someone to let you use a Juice or other such box, it might give you some additional insight into your truck's lack of power ... Jim Edited by: JEBar
 

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once i was pulling in the vermont hills this summer. had a bout 3000 miles on the odometer. gave it wide open throttle for the first time. got her going about 65 - 70 for a short stretch..got to the top of the hill and power loss occured. was coasting sown to about 55 ..took a minute or so..and then it was business as usual. i brought it to sevice mgrs attention. they scanned all the computerization...nothing showed up, however, they logged it with gm...maybe theres some breakin constraint built in ?? any ideas ??
 

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My California spec 03 went up the Cajon Pass (long steep grade) here in Ca. at 65mph towing almost 9000# stock. Mine was a brute from day one but it's a 6-speed. I flat run away from my neighbors v10 Ford and he tows a slightly lighter trailer than mine.
 

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I have no problems towing a 5200 lb travel trailer, plus camping gear, bicycles, firewood and passengers. I towed the first time with probably around 1500 miles on it when I brought the trailer home from the indoor winter storage facility at the local fairground. I've never had a moments notice of hesitation or lack of power with mine. Clean and crisp. I have not added modules or boxes, entirely stock, and as long as it runs the way it does, I don't see any need to add anything to it.


Certainly the suggestions offered, restrictions in the throttle, programming issues, clogged fuel filter, etc are all valid points to consider.
 

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How often did your engine fan turn on going up Cajon Pass? When I'm towing up a grade, mine will cycle on after about 3 minutes, then go for 3 minutes, then shut off for 3, etc...

And MAN, is that fan loud! First time she kicked on I backed off the throttle... lol
 

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correct me if i am wrong, but isn't power loss while pulling hard when new referred to as limp mode. i am not familiar with how that works. one guy told me that the computer lessens power so you don't break anything. is this true? if so, that could be the problem with low mileage trucks. MOTO HEAD says his was a brute from day one, but its a 6 speed. no such thing as limp mode with a manual, right?
 

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I don't remember how it cycled, but I remember it stayed on for a while near the summit. It was about 100 outside. The fan clutch didn't surprise me, I had an old Dodge motorhome that did the same thing. Boy does that fan work.
 

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Hi Folks, We have a new Sierra 2500HD, crew cab duramax. We bought it to pull an 8500 # 5er. We've only had it out 3 or 4 times, and we don;t have the kind of problems that Nickki Girl seems to have, but the power while good doesn;t knock my socks off. No problem easily pulling the 8500 lbs at 65, but reach a steep hill, and I'm doing 55 by the time I get to the top. If I absolutely jam my foot to the floor the Allison will downshift, and I can crank it back up again, but speaking to people before we bought, the comment was always "you won't even know the trailer is behind you." This truck is supposed to be able to pull over 13k #, so I would have though it would have an easier time. Now we only have 2000 miles on it, so perhaps it is a break in issue - am I just expecting too much?
 

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I only pull a 5K# boat/trailer a short distance to the lake and back but I did it several times a week most of the summer and noticed more power after 2k miles. It is all hills and curves on N Georgia mountain roads all the way so I think it was a good way to feel power. I think the difference from my first tow to the tows after 2K was significant.


Once I was satisfied that it was a break-in issue I added the Quad Stealth and on the 70hp tune I am really amazed! I can't wait to get my gauges so I can run the higher hp tunes!





 

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Thanks DMAX2DAMAX, I'll give it until the summer - in New York, my season for pulling a 5ER is rapidly drawing to a close. When the time comes, I'll get some advice on HP boosting.


Thanks again.
 

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While my Duramax can easily get up on top of a 10,000 lb. trailer it definately knows it's there. The people that tell you your truck won't know it's towing a heavy load are the same ones that tell you they get the same mileage towing as empty. Even a semi can feel a 10,000 lb. trailer. The truth is when towing my 26 Warrior trailer, slight grades don't even exist any more and I can do 65 in 6th gear with a/c and cruise control into a 30mph headwind and the truck is not even breathing hard. My old gasser wouldn't even pull overdrive into a headwind with a lighter trailer.
 

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Thanks Moto Head - I sort of thought as much. Since I have no previous experience, I think it is just folks who remembered sweaty fingers trying to make up a moderate hill in a gas truck. I guess slowing down to 55 from 65 on a steep one to them is like not knowing there is a trailer at all.


I do love the way the truck drives. I also drive a BMW 3 series, and I can tell you it is a close call which one I take out for a fun drive.
 

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Discussion Starter #20
Stringer nailed the problem right-on.


Upon the second trip to the dealer, the problem was solved.
It turned out that the dealer I purchased the truck from had the trailering wiring harness installed as aftermarket and an incompatible harness was installed. The harness installed was a 2002 model harness where apparently 2003 harnesses are not interchanable with 2001/2002.


I was told that the truck engine computer was reading from the harness that the trailer brakes were on even though they were not due to the mis-wiring. The engine was commanded into "safe mode" and the engine output was severly restricted.


The correct harness was installed and on our second trip hauling our 28 ft Outback TT, the truck towed like it was suppose to.
 
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