Duramax Diesels Forum Truck of the Week
Old 07-20-2019, 06:27 AM
06DDLBZ 06DDLBZ is offline
Join Date: Mar 2017
Posts: 34
Default In D truck wonít go above 2k, in P revs to 3500

Put a donor motor in the truck drove it for the first time and it would not get about 2k rpm. Itís shifts and still goes up and down the mph range drove it 80mph but feels like a limp mode. No CEL. When truck is in park I can stomp the pedal and redline it.

Truck has a Calvinís stage 5 with a goerend R converter that was restacked by the only Allison dealer here. Truck also has a GT3794VA on it thatís brand new.

Iím not sure where to start. I have a tech2. No codes in trans on ecm.

Fuel rail pressure is the same as requested.

Kory Willis tunes, had his TCM tunes but it TCM fried and just reprogrammed new TCM with GM Tech2 software. I wouldnít think this would be the issue since itís all new software on an all new TCM.

Anyone have any ideas? I donít know if itís a software or hardware issue.
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Old 07-27-2019, 02:15 PM
06DDLBZ 06DDLBZ is offline
Join Date: Mar 2017
Posts: 34

Turned out to be a bad MAF with a no CEL. Identified by tech2 reading.
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Old 08-07-2019, 08:05 AM
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HWI HWI is offline
Join Date: Feb 2016
Location: FL
Posts: 27

Same thing happened to me and it was also the MAF. I also had no CEL codes when I checked it with the tune installed, when I switched back to the stock tune it popped codes. I think the tunes change the MAF tables enough that it won't trigger a CEL, just a guess. But for anyone in the future reading this thread might be worth reverting to stock tune to see if you get a code.
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