HELP: 2015 LML Duramax starts and idles but will not take throttle
Need some help on figuring this one out. 2015 GMC Sierra 2500HD Duramax - 125K miles - Single owner - All stock. Historically this has been an intermittent problem that has occurred a half a dozen times or so now over the last 50K miles. It hasn't occurred in over a year (around 20k miles), until last night. It was driven to work in the morning (45 min drive), perfectly fine. Started the truck after work and it fired up and idled fine, but when attempting to drive it just sputters and bucks around when the go pedal is pressed. If you put it park and press the throttle it won't rev smoothly, and won't go to much more than 1300 rpm. It pulses like a smoker pulling tractor building power/boost before dumping the clutch.
In the past, stopping and restarting the truck has resolved the issue. Last night, around 25 restarts and it was still acting the same.
The truck has been randomly setting a P049D, that comes and goes. I checked the codes and this was the only code stored.
I suspected possible fuel restriction, but using a Kennedy Diesel test gauge showed only 2" of vacuum.
On a whim, I disconnected both negative battery cables. Cycled the ignition 2 times. Then reconnected the battery cables. The truck started and instantly ran perfectly. It would rev out smoothly and at 3K RPM I still only showed 4" vacuum on the test gauge. Drove the truck home and it ran flawlessly.
6:30 this morning, went out to head to work and it's doing the same thing. Not drivable. Before I try to 'reset' the thing again, what else should a guy check to pinpoint the issue with this animal?
2007 Classic CCSB LBZ
Last edited by paoutdoorsman; 12-20-2019 at 05:46 AM.