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6.7 Cummins Automatic High Idle Explained

mbarber84

mbarber84

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I frequently see questions from people wanting to know why their truck is automatically going into high idle. Everyone seems to focus on cold weather as the reason, but wanted everyone to be aware there are other things that will cause the truck to engage high idle as well. Please review this bulletin for High Idle triggers and their explanation IMG_5249.jpeg
 
The inverter one caught my attention as my 6.4 has the inverter, so will it trigger a higher idle speed on a gas truck?

I have also seen something about a winch mode for the Power Wagons.

I would like to see how to trigger both of them.
 
dieselscout80 said:
The inverter one caught my attention as my 6.4 has the inverter, so will it trigger a higher idle speed on a gas truck?

I have also seen something about a winch mode for the Power Wagons.

I would like to see how to trigger both of them.
Click to expand...

I would guess the inverter elevated idle is for the 2400w inverter, not the smaller 400w inverter.

A 2400w inverter at full low will draw ~200A and even with the 440A alternators idle output in a hot engine bay under load may be below 300A, so the elevated idle is needed for cooling air and amperage.



lol, someone at Stellantis didn’t do so well in math class….

IMG_8666.jpeg
 
dieselscout80 said:
The inverter one caught my attention as my 6.4 has the inverter, so will it trigger a higher idle speed on a gas truck?

I have also seen something about a winch mode for the Power Wagons.

I would like to see how to trigger both of them.
Click to expand...
The winch on a Powerwagon will idle the engine up.
 
The one that confuses me is in the super cold like below 0F the truck will start and then within a minute go to high idle. I would have through you want the fluids to come up a little bit before going straight to high idle from cold siting overnight in subzero conditions. I do not think my truck used to do this but when i got the latest engine update it now immediately goes to high idle below zero after starting. Might be to get more oil to the valve train faster but who knows.
 
jkempken said:
The one that confuses me is in the super cold like below 0F the truck will start and then within a minute go to high idle. I would have through you want the fluids to come up a little bit before going straight to high idle from cold siting overnight in subzero conditions. I do not think my truck used to do this but when i got the latest engine update it now immediately goes to high idle below zero after starting. Might be to get more oil to the valve train faster but who knows.
Click to expand...
If you’re using the correct viscosity (5w-40) you’re getting oil flow pretty quickly. That’s the whole point of the newer changes to recommended viscosity based on environmental temperature.

The block heater should be used as much as possible / whenever possible. Straight cold starting these trucks is hard on everything, especially your batteries.
 
I only use 5w-40 with being in Wisconsin. Block heater I usually plug in when it is negative temperatures but forgot and didn't last night. I did just change out my batteries to AGM's since my original ones started being weak in December and had to jump it once in the mid-December cold snap. The new AGMs really crank good.
 
jkempken said:
The one that confuses me is in the super cold like below 0F the truck will start and then within a minute go to high idle. I would have through you want the fluids to come up a little bit before going straight to high idle from cold siting overnight in subzero conditions. I do not think my truck used to do this but when i got the latest engine update it now immediately goes to high idle below zero after starting. Might be to get more oil to the valve train faster but who knows.
Click to expand...

These engines have idled at 1000 right after startup in extreme cold for at least 20 years. If the proper oil is used it flows just fine and the increased rpms promotes better cold cylinder combustion.
 
Did they change any of this for the 25 6.7? Ever since my dealer made some change to high idle with the scan tool where they said high idle was not enabled I've been getting high idle at 1500 rpm after remote starting. Tried to get them to change it back whatever they did as I think it shouldn't have been done, but they tried to tell me it's working correct and I don't know what setting to tell them to change back
 
tkabrick said:
Did they change any of this for the 25 6.7? Ever since my dealer made some change to high idle with the scan tool where they said high idle was not enabled I've been getting high idle at 1500 rpm after remote starting. Tried to get them to change it back whatever they did as I think it shouldn't have been done, but they tried to tell me it's working correct and I don't know what setting to tell them to change back
Click to expand...

I wonder if they did this to have a more reliable stationary idle operation. Those sound like ambulance settings where they idle for a long time - sometimes an entire shift. The alternator has to provide power for a lot of accessories and not soot up.
 
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