2015 2500HD Denali loss of power when towing

All Terrain Trav · February 10, 2015

20k miles, pulled 7x16 enclosed trailer like a champ from day 1 until a few weeks ago. Has began to struggle up even a minor hill. Seems to surge at times like something is physically holding it back. Downshifting doesn't seem to help. No check engine light and all gauges read normal.

CAtaylor · February 11, 2015

20k miles, pulled 7x16 enclosed trailer like a champ from day 1 until a few weeks ago. Has began to struggle up even a minor hill. Seems to surge at times like something is physically holding it back. Downshifting doesn't seem to help. No check engine light and all gauges read normal.

How does it run unloaded if you get in it? May be time to change the fuel filter if you haven't.

All Terrain Trav · February 11, 2015

Just tried it with no trailer just now and same result, but even more noticeable. Got up to about 20-30mph then floored it. Rpms went way up but didn't take off at all. Something is definitely no bueno. Fuel filter is one possibility, just wouldn't expect it with only 20k miles.

CAtaylor · February 12, 2015

Just tried it with no trailer just now and same result, but even more noticeable. Got up to about 20-30mph then floored it. Rpms went way up but didn't take off at all. Something is definitely no bueno. Fuel filter is one possibility, just wouldn't expect it with only 20k miles.

If the RPM's are up but not going I would think something torque converter related or trans slipping; the trans should throw a code though if it is limping. If it was the fuel filter the RPM's wouldn't climb, it would just fall down and never get there. Would also probably throw a rail pressure code. Might be time for a trip to the dealer, could be a lot of different things causing it with what you are describing

All Terrain Trav · February 13, 2015

Gonna take it to the dealer in the morning. I'm hoping it doesn't turn out to be a huge ordeal like my gut tells me it's going to be. My last trip there a few weeks ago for an oil change and tire rotation, they sent me on my way with 2 lug nuts barely finger tight. Didn't make it out of their parking lot (thank god) before the wheel nearly came off.

Gun Designer · February 25, 2015

20k miles, pulled 7x16 enclosed trailer like a champ from day 1 until a few weeks ago. Has began to struggle up even a minor hill. Seems to surge at times like something is physically holding it back. Downshifting doesn't seem to help. No check engine light and all gauges read normal.

Try turning off your traction control and see if it improves. I have an issue when it's cold and the traction control is on, loss of power, need to push throttle down around 25% to even make it move. Others have had response issues, GM says no solution. If it sounds negative, it's because I am. They print out a few TSB's saying its supposed to do that, and ignore what you tell them it's doing. Good luck, hope they do something for you, I know they didn't care about it for me. I also lost MPG which came back after turning it off.

All Terrain Trav · February 25, 2015

I took it in and they reset ecm/tcm and applied some software updates. It still drives like a big turd. Not even close to the power it had when new. Embarrassing when I go to pass someone at 50mph and the rpms are at 4k.

All Terrain Trav · February 25, 2015

Average mileage had also dropped by 2 mpg.

All Terrain Trav · March 1, 2015

I hope I've solved this. I installed a K&N drop-in/OEM replacement filter shortly after I bought the truck. After the last visit to the dealership didn't solve anything, I opened the airbox to check the filter just trying to narrow down the issue. In the bottom of the airbox was a sizeable puddle of K&N filter oil. K&N filters come pre-oiled out of the box, so I just dropped it in and didn't think twice about it. I've used their filters/CAI's on several other vehicles with no previous issues. After finding the puddle, I cleaned the MAF sensor, replaced the K&N with a Fram paper filter and took a peek at the throttle body. It's got a serious coat of sticky black gunk as far back as I could see. I'm thinking that the whole top end is gunked up with 20,000 miles of sucking excess oil from an over oiled filter. Maybe that would explain why it hasn't thrown any codes?

BigKahuna · March 2, 2015

There isn't enough oil on that filter to harm your engine, it will pass it. I bet cleaning up the MAF sensor and putting the stock filter back in will solve your problem.

All Terrain Trav · March 12, 2015

I paid for fuel system and throttle body cleaning at the dealership. Seemed to help for about 400 miles but now the issue is back. Sluggish and sometimes stumbling when taking off from a stop, no passing power. Tired of spending all my time at the dealership, and I'm sure they are tired of seeing me.

hegsz71 · April 1, 2015

Has it gone into regen lately? may want to look at the back end of things. Also have you done the fuel filter as stated above? I use to change my lbz every other oil change or every 6-8K miles.

All Terrain Trav · April 7, 2015

Not sure what you mean by regen. Haven't had a chance to get back to dealership yet, but the next step from what they say is to have me drive with the shop foreman riding shotgun with his laptop hooked up to the truck to try to figure out whats up.