05 2500 fast idle

[Byron]

I have an 05 2500 that goes to the fast or high idle feature even when the engine is warm. Does anyone know what sensors control the high idle feature?

 

[cerberusiam]

High idle is triggered by intake air temp. They will go to high idle if the ambient is too low irregardless of engine temp.



There are 2 air temp sensors on these trucks. The Air Intake Temp sensor is on the air box along with the ambient pressure sensor. The other sensor is part of the dual function MAP sensor and senses Intake Air Temp.



Not absolutely positive, but, I believe the one on the MAP is responsible for the high idle.



I temps below zero and a warm engine I have periodically seen mine jump to high idle on start up. Not very often but it can happen.

 

[AH64ID]

Sounds normal to me as well. If the ambient temp is below freezing, the coolant is below 200*, and the intake air temp is below 66* then after 2 minutes of stationary idle the rpms will ramp up to 1,000.



On startup there are 2 profiles.



~32*F and lower the rpms will ramp up to 1,000 after 2 minutes of stationary, uniterupted, idle.

~15*F and lower (I have seen it as high as 23*F) the rpms go to 1,000 as soon as the enigne starts .



And from what I have seen on my SGII you are correct, the MAP sensor is the sensor the ECM uses for computing fast idle and grid heater operation/timing.



With my winter front installed it is VERY rare to get the fast idle after the enigne is running becuase the IAT's don't drop below 66*F very easily.

 

[Byron]

Thanks for the info, I will have to pay more attention to the ambient temp when it does go to high idle. Sounds like it may be working as it should.

 

[Blakers]

Mine has been going to high idle even when it's 70 degrees out. It just stays up there during a stop - it does not ramp up after 2 minutes. Weird thing is it drops down to normal if the steering wheel is turned a few degrees, but does not drop when the brake pedal is pressed.



Any ideas?



Blake

 

[cerberusiam]

How about if you put it in gear and let the clutch just start grabbing?



There seems to be a program in the ECU that sense load and bounces the idle up to around 1000 automatically to compensate on clutch engagement. Periodically it will not idle down until the clutch is partially enaged then disengaged. Turning the wheel could be causing the same load on the power steering pump and effecitng it the same way.

 

[Blakers]

I wrote up a response, but the dumb thing lost it. I'll try to remember what I wrote...

I tried the clutch and it does seem to slow the idle down, as does tapping the brake sometimes. Moving the steering wheel does it every time. I don't think this is related to temperature or the low temperature high idle as it does not ramp up on its own like that does. This just idles down to about 900 after I take my foot off the throttle, instead of the usual 650 or 700. I also have the occasional rough idle that is only intermittent and can go away after driving down the road a half mile. Nothing consistent. Not sure if they are related.

Thanks.

 

[carl07230]

As winter is coming on I have played with the ideal of having the dealer turn my high idle feature on. As i let my 04 idle sometimes with the wife in it while i go into a store or hooking up a trailer. I was told it would be best to do this as not enough oil gets to the #6 cylinder while idleing at normal the normal rpm. Any input greatly appreciated. Please e-mail

 

[AH64ID]

It has nothing to do with oil circulation, there is 20+ psi at idle. . more on a cold motor.

It has to due with creating a operating environment that could allow incomplete combustion, which leads to cylinder washing.

 

[bsesby]

Dose anyone know how to get the high idle on my 04. 5 6spd to work?
I went to the dealer and had it "activated" Then they discovered that because its a manual that the computer thinks that it is not in Park and will not engage high idle... :-( so I thought about it and realized that it will still do high idle and when cold... humm so I went back to the dealer... and got a tech that know something more then the original one... I believe him when he said that his truck has more then 800 hp... after he padded me. He said that I need to trick one part of the computer... that activates the parking break light to flash, when not in "park"... the problem is he dose now know what what will happen when I drive if I trick the computer...

A little help!!!

 

[AH64ID]

You need to ground ECM pin #22, this tells the ECM you have a PTO and will allow you to use the cruise control fast idle. I have done this on my 05 and my dad's 06, takes about 5 minutes and has no negative effects.

part numbers and photo's in this thread.

high idle - Dodge Cummins Diesel Forum

 

[goodguys75]

You need to ground ECM pin #22, this tells the ECM you have a PTO and will allow you to use the cruise control fast idle. I have done this on my 05 and my dad's 06, takes about 5 minutes and has no negative effects.



part numbers and photo's in this thread.



high idle - Dodge Cummins Diesel Forum

so if I do the ground on pin 22, do I still need to take to dealer for the pto activation????2006 mega auto

 

[goodguys75]

so if I do the ground on pin 22, do I still need to take to dealer for the pto activation????2006 mega auto

now im confuesed... do i even need to do the pin ground, or just take to dealer to activate the high idle in the ecu???? 2006 mega auto

 

[Prairie Dog]

If it has the latest SW then you don't need to do anything more. Just use the cruise to raise the RPM's.

 

[AH64ID]

so if I do the ground on pin 22, do I still need to take to dealer for the pto activation????2006 mega auto

auto's don't need to ground the pin, just have it enabled.

 

[cerberusiam]

now im confuesed... do i even need to do the pin ground, or just take to dealer to activate the high idle in the ecu???? 2006 mega auto

The auto ground pin 22 with the neutral safety switch. If it has been enabled by dealer prep it may already work. Just try it.

 

[Bob V]

I think what has some confused is that there is two different high idles. One is done manually with the cruse control and my need more hardware and or software to work. There is also the automatic high idle that comes on when the intake air temps are low and engine is idling for about two minutes

 

[AH64ID]

I think what has some confused is that there is two different high idles. One is done manually with the cruse control and my need more hardware and or software to work. There is also the automatic high idle that comes on when the intake air temps are low and engine is idling for about two minutes

Correct. For the manual fast idle (not to be confused with only manual transmission), turn on CC and press set. If enabled rpms will jump to 1,100. RPM's can then be adjusted from 1,100 to 1,500 in 100 rpm increments with accel/decel. Cancel or the brake pedal will set the idle back to 750.



The automatic fast idle (not to be confused only with auto transmission) the rpms will jump to 1,000 after 2 minutes below ~32°F. Below ~15° the rpms will jump to 1,000 as soon as you start the truck.

 

[goodguys75]

auto's don't need to ground the pin, just have it enabled.

ok... cool. so have the dealer do the pto idle for it..... and I tried to do the cruise controll and then the accele button, but it did nothing. . is that how you activate the high speed idle. thanks for your info

 

[goodguys75]

ok... cool. so have the dealer do the pto idle for it..... and I tried to do the cruise controll and then the accele button, but it did nothing. . is that how you activate the high speed idle. thanks for your info

just read the above post for how you set the idle. . so im off to the dealer... thanks