I've been an automotive enthusiast since my first words as a child and have experience with engine swaps, electrical work and tuning traditional late model driveline systems (turbo BMW E21, LS6 powered GMC Sonoma to name a few). About midway through last year I grew tired of towing a 17' travel trailer with the Sonoma while my wife drove the kids separately so we settled on a 2011 Denali Hybrid purchased back in August which now has ~70,000 miles. Based on the complexity of the drivetrain in this truck I don't plan on doing much if any DIY, but am curious to monitor things by plugging in my HPTuners scan tool as well as purchasing a Scangauge to monitor battery PIDs. Will be even more interested to monitor things while towing (we now have a 24' travel trailer on queue for 2018).

So for my first question - I know the cold weather is harsh in general on efficiency performance and overall utilization of the advantages of the 2-mode, but out and about yesterday I managed to reach a stall point in terms of electrical ability to go in reverse. Without having any data monitoring plugged in when this happened, I have nothing but the feedback from in vehicle. I know reverse is electric-only and there are concerns with reversing up steep grades while towing, but I would not have expected to encounter this without a trailer on. So we were parallel parked on a city street and after about 4-6" of snow the previous night, a plow had pushed about 8" of snow up to the wheels on the Yukon. Hopped in, put in 4WD, went to reverse and the engine only revved to about 4k without traction control light blinking or wheels spinning (was not in auto-stop mode at the time, likely due to cold weather)...figured it was the reverse power-limitation, but was surprised it didn't even try to move. Dropped it into 4L and spun the tires to get out while still going in reverse. Question is, does this seem like normal operation in terms of being stuck in snow? I was surprised the electric reverse wasn't strong enough to back us out and I am now questioning the health of the battery. Luckily hybrid components still under warranty, but want to have this sorted out before I do any towing this summer.

 

Sounds like the packed in snow was a "wheel chock".


If the engine could spin backwards and make torque... this would not be an issue.

 

Yeah, that's essentially it. I just thought it was strange the wheels didn't spin in the snow in 4H. Oh well, not a big deal since 4L worked fine.

 

It's all physics, forces, and torque. Depending on the shape and density of the snow packed in, it might have been the equivalent of trying to go up an 8" concrete curb.