# High idle switch



## EricD701 (Jan 19, 2007)

I noticed on the build your own truck 2500HD there is an option for high idle switch.

What is that for?

Thanks,


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## CityGuy (Dec 19, 2008)

IMO it is for ideling the truck up to help it warm up faster.


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## ColliganLands (Sep 4, 2008)

on diesel its to run the idle around 1100 rpms to keep it warmer, prevent carbon buildup and helps with diesel wetting which can happen when a diesel just sits at normal idle for a long time
basically its so you cna leave your truck idling for long periods of time


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## CityGuy (Dec 19, 2008)

ColliganLands;731114 said:


> on diesel its to run the idle around 1100 rpms to keep it warmer, prevent carbon buildup and helps with diesel wetting which can happen when a diesel just sits at normal idle for a long time
> basically its so you cna leave your truck idling for long periods of time


You can also get this option for a 6.0 as i have it on my 08 6.o chev


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## EricD701 (Jan 19, 2007)

thanks for the info.. :salute:


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## JCI Trans (Oct 21, 2008)

Also useful if you are idling for a long time with accessories on, such as a/c, lights, etc. It makes more power from the alternator(s) All of our ambulances and fire trucks have this feature, wired to kick up automatically with the E brake


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## BigDave12768 (Nov 17, 2006)

if your Hemi is not turned on. Its Cruise control on then Set. Brings the CTD up to 1k to warm it up. Then automaticly shuts off becuase you have to put foot on brake to put in gear. Dealers can turn it on. I did mine with a Bully Dog


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## aeronutt (Sep 24, 2008)

Are you looking at 2500 Chevy or 2500 Dodge? I've noticed that my D-Max automatically cycles between high and low idle when it's warming up or sitting for a long period. I have no control over it other than it drops to low idle when I step on the brake. 

High idle is also useful if you have a PTO driven hydraulic pump for improved flow. The drivers side of D-Max motors already has drilled & tapped mounting brackets for an aftermarket hydraulic pump and there's a wired-in trick that automatically engages high idle when the truck is in Park or Neutral & the hydraulic pump is engaged. Having it available by flipping a switch would be sweet for externally powered machinery like a log splitter powered by the truck.


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## merrimacmill (Apr 18, 2007)

On my Duramax, it is controlled automatically, but I can select to never have it come on if I want by holding down the brake and hitting the gas 5 times with the motor off, and the key in the ON position. Is there a way to have it switched in my control? I agree that would be awesome.


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## BigDave12768 (Nov 17, 2006)

I know the old fords needed the Parking brake set for the RPM control to work. I am sure if you search the owners manual you can figure it out. I personal love my high idle. If I just started truck and left it for 10 minutes I would have no heat in cab. Even with high idle on for about 15 mins truck only hits 140 degrees and puts out ok heat, But its a nice feature to have enabled on a diesel. On a gasser I dont see the need that much. Here I found the lly Durmax one

The diesel engine has a high idle system to improve the warm-up time of the engine in cold weather conditions. This system allows the engine control module (ECM) to increase the idle speed above the normal calibrated value.

The ECM increases the idle speed using the following adjustments:


The fuel injection timing is changed.

The fuel injection quantity is changed.

The turbocharger vane position is commanded closed. the vane position will be farther closed than any other normal operating condition.

The instrument panel will indicate the high idle system is active one of two ways:


The Driver Information Center (DIC) will indicate an active high idle system on Light Duty Trucks.

An indicator lamp will flash on medium duty trucks.

High Idle Speed Enable and Disable

To enable or disable the high idle system perform the following procedure:


Turn the ignition ON with the engine OFF.

Depress the accelerator pedal to the floor and hold down.

While the accelerator pedal is depressed, depress the brake pedal 3 times in less than 8 seconds.

Release the accelerator pedal.

Start the engine.

When the procedure is followed the engine idle speed will slowly increased to the calibrated high idle speed. This is 1200 RPM for Light duty, and 1500 RPM for medium duty trucks.

The idle speed will return to normal if any of the following conditions occur:


There is brake, clutch, or throttle input from the driver.

The automatic transmission is shifted out of Park or Neutral.

The air temperature is more than 0 °C (32 °F).

The engine coolant temperature (ECT) is more than 68 °C (154 °F) The vehicle speed exceeds 0 MPH (0 km/h).

The high idle system will reactivate automatically when the following conditions occur:


The engine has been idling for more than 30 seconds.

The transmission is placed in Park or Neutral.

The vehicle speed is 0 MPH (0 km/h).

The ambient air temperature is less than 0 °C (32 °F).

The ECT is less than 68 °C (154 °F)

The brake, clutch and throttle pedals are not depressed.


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