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?

I wondering if it's the result of the system going through the regeneration cycle.

2edgesword wrote:I wondering if it's the result of the system going through the regeneration cycle.I didn't see any message on the info center about regen, I thought that too but pulling that much weight from Florence, SC today, I would think it would have burned the crud out of the filter?

2edgesword wrote:I wondering if it's the result of the system going through the regeneration cycle.regen won't trigger a power reduction.Did the Check engine light come on? If so did you read codes?Even if check engine light didn't come on, try reading codes and see if there are any pending codes or stored codes.Overheating, overtemp on the tranny will trigger power reduction, but it doesn't seem from your description that was the case.look in your diesel suppliment in the owners info, It has a section on what can trigger a power reduction.

That happened to me once. My problem was the thermostat.If your thermostat is not opening fully, maybe your engine got too hot on the uphill but was able to run without overheating on more level road.

A buddy had that happen while we were pulling car trailers from Crows Landing to Idaho coming up that big hill on the way to Reno from the Valley. We replaced his fuel filter and it was fine.

Duramax Power Reduction | Good Sam Community

ChuckSteed
Explorer
Jun 26, 2018
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
Explorer
Jun 26, 2018
You can also contact OnStar and they will read the code and tell you what the issue is.
hyattjlbb
Explorer
Jun 25, 2018
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
Explorer
Jun 23, 2018
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
Explorer
Jun 23, 2018
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
Explorer
Jun 23, 2018
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
Explorer
Jun 22, 2018
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
Explorer
Jun 22, 2018
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
Explorer
Jun 21, 2018
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
Explorer
Jun 21, 2018
Duramax trucks limit vehicle speed, not engine power, if there is a def issue.

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