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Discussion Starter #1
We traded our 1997 1500 Suburban for a 2003 GMC Sierra 2500HD, Duramax Diesel, 4x4, 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's 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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Well, normally I would give the answer, just let it break in.. give it some time.. But there is no way a 1/2 sub is gonna out tow a 3/4 ton diesel. I do have to think that there is some issues in there, perhaps a fuel filter? Maybe the truck had a bad load of fuel in it. That is the place I would start, regardless of the low mileage. How does the truck run empty? Does it compare to a similer truck? I do think that there may be an issue there, but I would start with the fuel filter. See how it goes after that and let me know.
 

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Discussion Starter #3
Thanks for answering. The truck seems to run fine without a load and does 75-80 no sweat.


If it were a fuel filter, wouldn't the conditions exist with load as without load where performance should be the same? I think its got to be something else then the filter.


We've only had two tanks of gas but again, there shouldn't be a difference in engine performace between load and no load right?
 

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You are correct on the load/no load, the only reason I can see the difference would be that the engine has to work harder and will demand more fuel when its working, no load, the demand is less and flow may be sufficent. Its a cheap thing to do and it cant be done enough if you ask me.
Its really hard to pinpoint a reason for the percieved lack of power with out driving it with a tech-2 under those conditions and seeing what the data stream is...
 

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Discussion Starter #5
The problem was solved.
it turned out that the dealer 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 breaks were on even though they were not due to the 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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nikkigirl, thanks very much for the update! I will store this one in my memory banks to remember. This trading knowledge thing works both ways!


Eric
 
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