Duramax Power Reduction

[hyattjlbb]

Not sure if this is the right place to post so admin please move if needed.

96 degrees, mountains of North Carolina/Virginia. Climbing around Fancy Gap on I-77 and with no warning truck says "power Reduced". Dropped to 15 mph towing the below 5vr up the rest of the hill. Gauges all good, DEF good, fuel filter good. Nothing giving me any warning or explaining the power reduction.

Could it be that the heat and climbing just put the system in to reduction to protect it?

I shut of the engine later at the nearest exit/gas station and it reset and pulled fine the rest of the 30 miles to Wytheville KOA where we are overnight tonight.

Any ideas?

[ChuckSteed]

On a duramax if the MAP sensor gets a bit of gunk on tip of sensor truck goes into limp mode. 25 mph max speed. Code reader would give you the code and it’s one 10 mm bolt and 30 secondsnto wioe tip and reinstall and clear code and get out of limp mode. Just an example.

[ksss]

You can also contact OnStar and they will read the code and tell you what the issue is.

[hyattjlbb]

ChuckSteed wrote:
Buy a decent code reader and keep it in your truck. Sooner or later you will need it and be glad you got it.

Totally agree, especially after this little episode. Would have been handy and could have "googled" the code!

[ChuckSteed]

Buy a decent code reader and keep it in your truck. Sooner or later you will need it and be glad you got it.

[hyattjlbb]

And it was not a DEF fill issue at all as I filled prior to,leaving on our trip and it said “OK” when I was trying to diagnose the issue. Did not receive any of the normal DEF warnings either. Could it have been something else with the DEF system? Possibly.

[hyattjlbb]

bartlettj wrote:
Duramax trucks limit vehicle speed, not engine power, if there is a def issue.

Possibly but the truck tells you “Reduced Engine Power” when it happens. Going up the mountain I could get about 16 mph, coming down the ramp to get off the interstate I had 40 mph so not a speed issue but a power plant issue.

[lee_worsdell]

My 13 duramax did the same thing on the same hill. Thru code so I just happened to have a code reader. It was something to do with turbo vein positioning.I cleared code and continued. A little slower this time code never come back all the way home to Ontario. Did trade truck for a 17 now

[bartlettj]

ACZL wrote:

bartlettj wrote:
Duramax trucks limit vehicle speed, not engine power, if there is a def issue.

Not to be a smart azz, but are you sure about this? D-maxs may be entirely different animal compared to semi engines. As I mentioned in my post, w/ our semis, if a DEF problem is serious enough, it will derate the engine power. Will take a whole lot longer to get up to speed and puke on hills. If problem is bad enough, a red/shut down light comes on and gives you not a whole lotta time to get onto the shoulder before the engine shuts down. Safety measure perhaps to protect the engine, but the not safest feature in my book just in case you can't get to shoulder right away.

Semis and pickups are not the same. I'm going by what my owners manual says. If there are problems with the def on a GM pickup, you get speed limit warnings and enforcement,but you have a fair amount of time before it will limit you to 4mph.

[ACZL]

bartlettj wrote:
Duramax trucks limit vehicle speed, not engine power, if there is a def issue.

Not to be a smart azz, but are you sure about this? D-maxs may be entirely different animal compared to semi engines. As I mentioned in my post, w/ our semis, if a DEF problem is serious enough, it will derate the engine power. Will take a whole lot longer to get up to speed and puke on hills. If problem is bad enough, a red/shut down light comes on and gives you not a whole lotta time to get onto the shoulder before the engine shuts down. Safety measure perhaps to protect the engine, but the not safest feature in my book just in case you can't get to shoulder right away.

[bartlettj]

Duramax trucks limit vehicle speed, not engine power, if there is a def issue.

[ACZL]

On our semis, reduced power is usually the result of the DEF system having a issue.

[bartlettj]

hyattjlbb wrote:
Thanks all! Sounds like several possibilities here. When I called my GM shop back home mech mentioned that it could have been a partial collapse of the fuel line with the warm weather and fuel, etc. Last night and again this morning doing my checks and everything is fine, gauges, pressures, etc and the engine light went out. Guessing that code is gone now with the engine light? Either way, on the road this morning while it is cool to cross into Ohio from Charleston WV. Hope it was a fluke and we will get it checked when we get home. Thanks again!

Even if the engine light is out, the freeze frame data is still stored in the ecu so with a good code reader you can still find out what it was for.

[steadfastrock]

Had that happen on our old 2011 GMC going up a steep grade here in Idaho. Dealer said that it was a known problem and the fix was to flash new firmware to the computer. No problem after that with that truck.

[hyattjlbb]

Thanks all! Sounds like several possibilities here. When I called my GM shop back home mech mentioned that it could have been a partial collapse of the fuel line with the warm weather and fuel, etc. Last night and again this morning doing my checks and everything is fine, gauges, pressures, etc and the engine light went out. Guessing that code is gone now with the engine light? Either way, on the road this morning while it is cool to cross into Ohio from Charleston WV. Hope it was a fluke and we will get it checked when we get home. Thanks again!