Hesitation,then surge

[RocketCrockett]

I recently had my 2020 Denali with 3.0 duramax in for a problem with my cruise control. They replaced several parts,and among them was the engine control module. When I got the truck back, the cruise was working,but engine performance seemed a little weird. When I take off from a dead stop,engine is a little lazy until I hit 1500 rpm, then it lurches from 1500to 2000 in an instant and jerks your head back like my old muscle cars when the 4bbl kicks in. I also notice more turbo noise when it is spooling down at low speeds. The other thing that happened was the def speed warning came on,and I know the def tank was over a half full when I took it to dealer. I put one jug(2.5 gal) in it. When the warning turned off after about 5 miles, I checked the gauge and it was showing completely full. A trouble code came up and after checking it was P2BAA. NOX high. Any ideas from you guys? Fuel mileage seems to be the same. I’m a little hesitant to take it back to dealer for fear they’ll screw something else up.

 

[RocketCrockett]

I recently had my 2020 Denali with 3.0 duramax in for a problem with my cruise control. They replaced several parts,and among them was the engine control module. When I got the truck back, the cruise was working,but engine performance seemed a little weird. When I take off from a dead stop,engine is a little lazy until I hit 1500 rpm, then it lurches from 1500to 2000 in an instant and jerks your head back like my old muscle cars when the 4bbl kicks in. I also notice more turbo noise when it is spooling down at low speeds. The other thing that happened was the def speed warning came on,and I know the def tank was over a half full when I took it to dealer. I put one jug(2.5 gal) in it. When the warning turned off after about 5 miles, I checked the gauge and it was showing completely full. A trouble code came up and after checking it was P2BAA. NOX high. Any ideas from you guys? Fuel mileage seems to be the same. I’m a little hesitant to take it back to dealer for fear they’ll screw something else up.

I forgot to mention I have 54,000 miles on the truck.

 

[gemarsh]

I'm wondering if the new ecm is learning.

Are you saying you didn't have throttle lag before the repairs or that the throttle lag is way worse?

How many miles have you put on the truck since the NOX high code?

 

[Bob]

I recently had to put our 2023 LTZ in the shop for no cruise and put hands on wheel command. They had to reprogram the computer. 4 modules had to be reprogramed with a cost of $250 each. Lucky for me it was under warranty. The first problem we had was the radio quit. again 4 modules had to be reprogrammed. We have 9000 miles on the truck. I wish auto stop would go out.

 

[RocketCrockett]

Yeah,throttle lag is worse,then goes from 1500-2000 jerking the truck like a two stroke hitting the power and on a dirt bike. . I’ve only put about 20 miles on it so far. I cleared the code after adding def,once the warning went away. I checked yesterday with scan tool and no codes have come back. Maybe you’re on to something about the learning. . The turbo is definitely louder from the intake,especially at idle and spool down from low rpm’s. Mileage seems to be the same. Will try to put some more miles on and see. Leave in about 3weeks to drive from Georgia to Maine,so I want to feel confident trucks ok before leaving.

 

[RocketCrockett]

I recently had to put our 2023 LTZ in the shop for no cruise and put hands on wheel command. They had to reprogram the computer. 4 modules had to be reprogramed with a cost of $250. Lucky for me it was under warranty. The first problem we had was the radio quit. again 4 modules had to be reprogrammed. We have 9000 miles on the truck. I wish auto stop would go out.

Yeah,I couldn’t deal with the auto stop any longer. Bought the module to disable it. Best money I spent.

 

[Bob]

Which module did you get? How did it install?

 

[RocketCrockett]

There are several brands out there,the one I chose was”Autostop Eliminator “. Was $99.00. I have a Denali with center console. You have to remove the center console and face on center of dash to expose the back of auto stop button. The module plugs inline to the button and connecting harness. You can find videos on YouTube that show exactly where to pry on the plastic trim so you don’t break any clips. The module will completely disable it,or with a push of the button, you can turn it back on like stock. Had mine in truck for 4 years now with no problems. I got sick of having to press that button every time I crank up!!! I’ve been a mechanic all my life and I don’t care what anyone says, it’s hard on the engine to shut off at red light and crank up with your foot on the gas,immediately under a load. Just my opinion.

 

[marottpa]

I'm running into the same problem with my yukon xl diesel. We had an issue with the emissions system, took it in, they fixed whatever they fixed but then had to put a new computer in because the old one "bricked". Started driving it after we picked up and with a consistent throttle pressure you get nothing nothing and then a surge. It's turbo lag for sure, just not sure why. Maybe a waste gate or something, I need to take it back in. Did you ever get an answer on your truck?

 

[RocketCrockett]

I'm running into the same problem with my yukon xl diesel. We had an issue with the emissions system, took it in, they fixed whatever they fixed but then had to put a new computer in because the old one "bricked". Started driving it after we picked up and with a consistent throttle pressure you get nothing nothing and then a surge. It's turbo lag for sure, just not sure why. Maybe a waste gate or something, I need to take it back in. Did you ever get an answer on your truck?

I took truck to dealer and performed the module relearn. Picked truck up and it was running great,with no hesitation. Put about 500 miles on truck and it went back into limp mode again. Took back to dealer. They said it needed an actuator and would have to order it. Got it in and replaced. Didn’t solve the problem. GM said to replace whole turbo assembly. Unfortunately they’re on back order. Eight dealers in the US had one,but wouldn’t let them go because they were holding it for their customers. . Finally this dealership got one through “SPEC”. They say truck should be ready tomorrow. I’m keeping my fingers crossed. . Keep in mind ,we’re 1300 miles from home,had to get a rental car(about$800.00 so far).

 

[marottpa]

Dang that sucks! When you say it went into limp mode, does that limit your mph or does it limit power? I've only experienced the mph limitation when I had that emission system fault. Sounds like I'm headed down a similar rabbit hole

 

[RocketCrockett]

Got a message on dash saying that in 175 miles speed would be limited to 65 mph. Funny thing is when the code set truck was instantly down on power and would only run 53 mph with foot on the floor. I keep a scan tool in truck,so I tried clearing the engine trouble code. I was able to clear code and light,and the truck was running fine. Only problem is warning message was still on dash with mileage counting down. As soon as I shut truck off,light would come back on and were back to 53 mph.

 

[A1fromday1]

Just wanted to check if anyone figured out for sure what may be causing the lag? Mine seems to be getting worse on it. At take off it feels real weak for a few seconds then takes off. ECM was recently replaced due to a starting issue but that was over a month ago. Average fuel mileage has dropped by a good 3MPG this summer as well over previous summers.

 

[A1fromday1]

I guess we'll see if it's related to the lag but mine was also making noise like old school diesel clatter on light acceleration and I had diesel tech at dealer ride with me and he's thinking it's timing chain stretch. No check engine lights. Going in tomorrow to have timing chain replaced. Motor out repair that's luckily covered by warranty. They are going to do the oil pump belt while out and I just have to pay for the belt. Fingers crossed.

 

[RocketCrockett]

I guess we'll see if it's related to the lag but mine was also making noise like old school diesel clatter on light acceleration and I had diesel tech at dealer ride with me and he's thinking it's timing chain stretch. No check engine lights. Going in tomorrow to have timing chain replaced. Motor out repair that's luckily covered by warranty. They are going to do the oil pump belt while out and I just have to pay for the belt. Fingers crossed.

Mine has always had engine clatter at light,no load acceleration. If I press on the pedal just slightly,it goes away completely. I’ve got about 4000 miles since turbo assembly was replaced and no problems. the funny thing is with original turbo,engine was quiet,no exhaust noise or turbo noise. Now the engine has a throaty sound and you can hear a little bit of turbo moan at1600-2000 rpm under load. It sounds good,definitely something different with this turbo.

 

[marottpa]

I have this same thing, happens especially in the morning when the car is cold and when I’m going up a slight grade. To me it feels related to the turbo, waste gate or something like that. Maybe staying open or closed I’m not sure. They replaced the valve body in the transmission but did not do a thing to resolve the issue. Back at the dealer now waiting to hear

 

[RocketCrockett]

I have this same thing, happens especially in the morning when the car is cold and when I’m going up a slight grade. To me it feels related to the turbo, waste gate or something like that. Maybe staying open or closed I’m not sure. They replaced the valve body in the transmission but did not do a thing to resolve the issue. Back at the dealer now waiting to hear

Are you referring to the rattle(like spark knock in a gas engine) or the surge? If it’s the rattle,my personal opinion (mechanic for 50 years now) is it’s just like a lean,no load,high vacuum timing period. The engines are run so lean to pass emission standards,even the diesel’s. If it is rattling all the time,then that’s a different story. That would be a problem. Mine has 60,000 miles on it now, and has always had the slight rattle under very light acceleration at low speeds. If you’re referring to the turbo lag,then jerk, mine also started after taking it in to the dealership for a problem with my cruise control. 50.000+ miles and never had any problems with the engine or turbo. Dealership replaced a couple of computer modules,one of them being the “ECM” engine control module. Still not sure why the cruise not wanting to set would require the eco to be replaced. I think sometimes techs just throw on parts until something finally solves the problem and yes,I have worked with some of those tech's. Anyway,when I picked the truck up it had the lag and then jerk forward. Unfortunately I was leaving for a 1,300 mile trip 2 days later and could not take it back to them. I left for my trip hoping it was just a learning issue with the module and that it had to relearn my driving style. That was not to be and we barely made it to our destination in limp mode. The rest is written previously on this forum. Sorry for being so long winded,but hopefully answered your question.

 

[marottpa]

Are you referring to the rattle(like spark knock in a gas engine) or the surge? If it’s the rattle,my personal opinion (mechanic for 50 years now) is it’s just like a lean,no load,high vacuum timing period. The engines are run so lean to pass emission standards,even the diesel’s. If it is rattling all the time,then that’s a different story. That would be a problem. Mine has 60,000 miles on it now, and has always had the slight rattle under very light acceleration at low speeds. If you’re referring to the turbo lag,then jerk, mine also started after taking it in to the dealership for a problem with my cruise control. 50.000+ miles and never had any problems with the engine or turbo. Dealership replaced a couple of computer modules,one of them being the “ECM” engine control module. Still not sure why the cruise not wanting to set would require the eco to be replaced. I think sometimes techs just throw on parts until something finally solves the problem and yes,I have worked with some of those tech's. Anyway,when I picked the truck up it had the lag and then jerk forward. Unfortunately I was leaving for a 1,300 mile trip 2 days later and could not take it back to them. I left for my trip hoping it was just a learning issue with the module and that it had to relearn my driving style. That was not to be and we barely made it to our destination in limp mode. The rest is written previously on this forum. Sorry for being so long winded,but hopefully answered your question.

It's more of a fluttering sound, that's the best word I can use to describe it. Different than the cold diesel rattle. Maybe a blow off valve just constantly fluttering and the car literally sputters trying to deliver power. This is all at maybe an 1/8 throttle, just tipping in. It all started with an emissions issue I mentioned in a previous post where mile speed was limited to 65 then 55. Brough it to the dealership, they fixed the emissions issue but in the process they also had to replace the ECM and ever since then it has not run correctly. I feel like the dealer told me at one point that each engine is tuned a little bit differently from the factory and maybe when they switched the ECU's something didn't translate. I have no idea and unfortunately they don't either right now I'll keep you posted if I find a solution.

 

[RocketCrockett]

It's more of a fluttering sound, that's the best word I can use to describe it. Different than the cold diesel rattle. Maybe a blow off valve just constantly fluttering and the car literally sputters trying to deliver power. This is all at maybe an 1/8 throttle, just tipping in. It all started with an emissions issue I mentioned in a previous post where mile speed was limited to 65 then 55. Brough it to the dealership, they fixed the emissions issue but in the process they also had to replace the ECM and ever since then it has not run correctly. I feel like the dealer told me at one point that each engine is tuned a little bit differently from the factory and maybe when they switched the ECU's something didn't translate. I have no idea and unfortunately they don't either right now I'll keep you posted if I find a solution.

I bet they end up replacing the turbo before it’s all said and done. They replaced turbo actuator and did a range of motion relearn on mine and still didn’t fix the problem. GM has had a problem with the mounting bolts on the actuator getting loose and allowing the the actuator to get out of calibration. That was not the case with mine,but I read a service bulletin addressing this issue.

 

[A1fromday1]

Update: dealer called and said they found more issues when they went to do the timing chain. Head gasket had a leak and the turbo was going out (which that makes sense as it felt like it might have been turbo lag). Will be next week sometime before it'll be done.