2005 Allison 1000 going into limp mode, help

firedreamer · April 28, 2019

OK folks need some help. Have owned a 2005 3500 Silverado dully for 3 years without problems. 163000 miles on the Duramax / Alison 1000 setup. The last month or so it has gone into limp mode but only when I start to tow our 5th wheel. It will reset if i pull over and turn it off for a min or two but I have only let this happen about 3 maybe 4 times. It will drive all day long and hundreds of miles at any speed without towing. So I had the error codes pulled and get the classic P0700 from the ECM and so I know that mean a internal trans error code and the local Alison shop will pull that code for me this coming Tue for $75 versus the Chevy dealers $100.
So here is my question, Is there anything that could possibly be wrong inside the trans or maybe the TCM needing to be re-flashed or replaced or something that could cause this without needing to do a complete rebuild? I just don't have the $ to do a complete rebuild right now, but something short of that , maybe. I don't mind spending the $75 if there's any chance they could find a cheap repair but if there's no chance at all short of rebuild and it's drive it for now without towing or rebuild I would rather not spend the $75 right now. THOUGHTS ?
Thanks for your suggestions

davester · April 28, 2019

If there is a parts store, they may/should have a code reader that can read tcm codes (maybe phone ahead/around for it), and they generally do it for free...

I don't know much about the failure modes of the Allison, you could also try asking on the dieselplace forum, they seem pretty knowledgable about duramaxes and the allison transmission.

firedreamer · April 28, 2019

Thanks thats what I did do to get the ECM code of P0700 thats simply tells me there an error code in the trans computer and the parts stores cant / wont do that

davester · April 28, 2019

If that' all the parts store code reader can do, and this is a truck you plan on keeping for awhile, then I would suggest buying a better code reader rather than coughing up $75-100 every time. Something like, say Autogenuity w gm enhancement, which is software that runs on a windows laptop, with a usb-odbii cable, which can read codes from every computer in your truck (there are more than 10)... It also can help you perform a variety of testing and diagnostic procedures, such as bleeding the ABS system for example, which you need a more advanced setup to do.

firedreamer · April 30, 2019

OK, here's the codes i got today from the trans shop today ....
P0670 glow plug control circuit ( thats been in the History for awhile)
P1093 fuel pressure low while enrichment returned

the tech said he cleared the codes and then drove the truck and was able to recreate the problem when he "got on it pretty good." Then he got these codes. So I'm thinking it's more likely a fuel pump problem? yes /no? It's going into Chevy dealer tomorrow for them to tell me whats wrong and cost to repair.

firedreamer · May 2, 2019

A bad fuel pressure regulator, thats what dealer found so pretty easy fix when they get the part. may take a few days tho GM does not have one but some other dealers in the region do. thanks for all your input folks