Hi, new here, so I hope I'm in the right place for this question. I'm actually writing for my dad - he has a 2007 (early model year, before the body style change) 3500HD dually crew-cab with the duramax and allison 6 speed transmission. He hauls campers and camp trailers around the pacific northwest for a living, and is having problems getting up hills without tripping the limp mode. Mods: 4" exhaust from turbo back at 275,000 miles, 45 hp power chip at 275,000 miles, (both done at a pro shop). Maintenance: Oil change every 7500 miles religiously, tranny filter changed and serviced every 50,000 - very little if any shavings, fluid is never burnt, fuel filter replaced every 15,000. At 37,000 miles, it went into limp mode for the first time. The fuel filter was replaced, and the tranny serviced. It has been to dealers and shops all over Idaho and Washington, and they all say it is a fuel problem. at 300,000 it went back to the dealer and they replaced the strainer and pick-up tube in the fuel tank. Truck runs awesome - 100 mph+, hard acceleration or slow, with no limp mode when empty - but when loaded, limp mode. After being in to the dealer this last time, the truck didn't even make 50 miles loaded before triggering limp. When it goes into limp mode, the check engine light comes on, and he only can get about 2,000 rpm, and the tranny sticks in a lower gear. Stopping and shutting the truck off alleviates the problem temporarily, but it goes limp again soon after. The tranny shifts great, no slipping that he can notice, and the truck - out of limp mode - runs like new. My dad takes very good care of his equipment, and the truck looks and drives showroom new after 300,000 miles. He has spent almost 5,000 bucks trying to fix the problem and it is still not fixed. Needless to say, we are at our wits end. We are both very mechanically inclined, he has wrenched on rolling iron his whole life, and I was a mobile diesel mechanic - (semi trucks) - but we are both completely and totally lost. Any help anyone could give us is very much appreciated - we are thinking it is something with the tranny, hopefully something we can do ourselves.
Allison 6sp: Please help!!! 2007 limp mode...
- Thread starter jmholsbeck
- Start date
Do you have any codes coming up. Could be a fuel issue might need to do a bottle test the fprv leaking fuel into the return on high demand. But dtc codes from the engine light would help alot here.
He's on the road right now, but the next AutoZone he sees, he'll pull in and either have them pull the codes (I think they still do that for free)- he was just getting started again after having been in limp mode - or get a reader and pull them. I'll post them asap. Thanks!
Also if it is a trans code most scanners will not pull tcm codes only a Tech2 from the dealer or efi live and I think PPE pulled them when I ran it. If he gets a dtc of a P0700 its a trans mil light then there should be more P07XX code if its fuel might be P0087. Here is the link to the list of DTC's codes http://www.duramaxdiesels.com/forum/showthread.php?t=8120
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He had the work done at a speed shop, he doesn't have a tuner, just had the programming reworked to give an extra 45 hp is what he said. I'm not too familiar with this shop, but they did all the work, including the exhaust. Does that even sound right?
Was it a dealer that bumped the power up 45 hp or a shop with a efi live or hp tuner.I would call that shop and find out what they did to get the extra power.
I'll call them right away, and see what they did. Something interesting that he just told me - when driving in the winter, it hardly ever goes into limp mode, except when pulling a long grade. It happens far more frequently in the warmer months. I'm working on getting the codes, and I will call the speed shop and see what they did to ramp up the power. Thanks so much for all the replies!
Before i put a race valve in my truck it would only limp when it was 90*+ and WOT... with that many miles on it, it could very well be the FPRV has finally worn out and it could be popping.
Sounds like an engine limp to me. A transmission limp will not limit the engine to 2000 RPM. You need to hook up a gauge to the test port next to the alternator. It shouldn't pull more than 12 inHg at the highest fuel demand situation. If you put the truck in neutral and bring it up to redline, it shouldn't go above 5 inHg. Also, do a bottle test to see if the FPRV is slightly leaking. You may also want to check injector return rates.
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This thread is worthless without codes. I do not understand why some people will go to all the trouble to post a long and drawn out scenario and not post the codes. We do not have a cristal ball and we are not there with the truck to feel what it is doing.
Post the codes.
Remember one thing. When the time comes to diagnose properly; have the truck scanned with a professional scanner or EFI. Little chicken shit hand held readers may not pick up the proper codes. If there are more than one code, the sequense of the codes can lead us to the problem. Do it right.
Post the codes.
Remember one thing. When the time comes to diagnose properly; have the truck scanned with a professional scanner or EFI. Little chicken shit hand held readers may not pick up the proper codes. If there are more than one code, the sequense of the codes can lead us to the problem. Do it right.
I'm sure we all can figure out that it is a p0087 code, jezz all this code stuff is turning people into parts exchangers not mechanics..
Here is a link that you should look at, it tells you how to do a bottle test. http://www.duramaxdiesels.com/forum/showthread.php?t=1995&highlight=bottle+test
It would be better to make sure its the problem before throwing a new fprv on just hoping to fix it, because many people seem to have trouble getting them to seal up again after removal
EDIT: make sure you plug the other return line side of the U shaped fuel line with a bolt or something, otherwise you'll have fuel coming out of it and smoking up the engine bay. That may cause you to freak out, I know I did lol
Here is a link that you should look at, it tells you how to do a bottle test. http://www.duramaxdiesels.com/forum/showthread.php?t=1995&highlight=bottle+test
It would be better to make sure its the problem before throwing a new fprv on just hoping to fix it, because many people seem to have trouble getting them to seal up again after removal
EDIT: make sure you plug the other return line side of the U shaped fuel line with a bolt or something, otherwise you'll have fuel coming out of it and smoking up the engine bay. That may cause you to freak out, I know I did lol
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Well, I finally did get the codes when he got in off the road, he spends so much time hauling out there it's tough to get the time, so excuse the **** out of me for trying to help him out in advance of getting the codes. I never asked anybody to have a crystal - not spelled "cristal" by the way - ball, I was just looking around to see if anyone had any advice, or if anyone had run into the same thing, so I could be prepared when I did get the codes. I'll be taking my questions elsewhere from now on, so you can go back to being a prick.
Thanks for everyone else's help, it is greatly appreciated, and I sincerely appreciate the good advice I got from the rest of you guys.