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Old 05-01-2017, 12:36 AM   #1 (permalink)
Gear Grinder
Join Date: Oct 2016
Location: San Francisco Bay Area - CA
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2003 LBZ Suburban - Dual Fuel Tank Help

Hey guys,

I can use some help. I have researched and learned so much online the last couple of months but I still can not figure out my issue.

I have a 2003 Suburban that has a LBZ installed in it. Everything is fine with the install with the exception of the dual tank tuning. This is where I can really use some help.

I had DuramaxTuner install a dual tank setup when I purchased EFI Jack DSP5 Tunes from them. Boy did the tunes make a huge difference in performance! Having the dual tank programming added, the dual tank function does not operated. I have went through all the wiring, fuel level sensors and the transfer pump, and everything checks out 100%. I checked the operation of the pump and fuel level sensors at the ECM; both fuel level sensors read at the ECM and I can manually run the transfer pump from the ECM as well. Even with everything appearing to be installed correctly the aux fuel tank gauge does not change the dash fuel reading when I manually change the aux tank float position nor does the dash gauge change when I unplug the rear sending unit. Also, I get no trouble codes for the dual tank setup not functioning. All this is telling me that the dual tank tune does not exist, right?

So I think it can be an issue with how DuramaxTuner installed the dual tank tune or an issue with my ECM. Is there anything else it could be? Bob/Jim at DuramaxTuner believes the dual tank tune is programmed correctly but it just does not add up.

I would appreciate any help on getting this resolved.

Thanks in advance.

2003 Suburban with a 2007 LBZ Duramax Engine
EFI DSP5 Tuned
4:10 Gears
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Old 10-12-2017, 12:31 AM   #2 (permalink)
Diesel Head
Join Date: Mar 2007
Location: Elk Ridge Utah
Posts: 619
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You need to have your own efi live. The os of the ecm might not be playing nice w the os of the bcm ipc. I had to try a couple different ecm tunes before mine worked

1972 4X4 blazer with a 6.6, parked and eng yanked
2007 Suburban LBZ/LMM Lifted on 36" BFG MT
New toy 71 4x4 LB project under way


.!.. OBAMA
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Old 10-14-2017, 08:37 AM   #3 (permalink)
Diesel Head
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Join Date: Dec 2003
Location: Ontario Canada
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Ontario Diesel Place Chapter Member

Did you rewire the aux fuel tank relay? You said changing the float arm of aux doesnt change gauge... Was this you manually lifting arm? Dont forget a sudden change in level the ecm wont register it. You would have to shut key off, change level, turn key back on.

I cant see nick not sending you a dual tank file. Hes the guy on that. Could be a OS prob ask stated above. Bestvis to use efilive to see if both tanks are registering
2008 gmc sierra 3500HD LMM bds 7" 37" AT3Ws,built trans,possible s475 over stock build,
2004 Suburban 2500HD, 4x4, LBZ/Allison, DSP5, MBRP,
2005 Hummer H2, Blk on Blk, LLY/Allison 4x4, EFI Live by ME!
2018 Tahoe premier RST (future Iml or l5p?)
2001 GMC Yukon Denali XL 2500HD 4x4, LB7/Allison EFI Live DSP2 by Theferminator, MBRP,
2003 GMC 2500HD 4x4 CCSB, LLY/Allison, DSP5 EFI live by Idaho Rob, 5" MBRP exhaust, 6" pro comp lift, 35" nittos, LBZ mp
2003 GMC Yukon XL, 2500HD, 4x4 LBZ/Allison, EFI live by Idaho Rob
2003 GMC Yukon Denali XL 2500HD 4x4, LBZ/Allison, EFI live DSP5 by Theferminator
2006 GMC 3500HD C&C, LBZ/Allison, 14' aluminum dump bed
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