I have an '06 3500 4x4 with 34k miles that has recently started idling high, 1000 rpm's. It only does it maybe 2-3 times per day for no apparent reason. Took it to the dealer and drove around with the Tech with the computer hooked up and of course it wouldn't do it. Tech says he can't do anything because no codes are thrown and he has to see it to diagnose it. On the way home from the dealer it did it twice and the dash made a "ding" sound but no lights came on.

Can anyone advise on what this could be?

 

The automatic high idle is a built in feature that activates when the engine is at an idle and the ambient temps below 30 degrees. Its normal.

That being said, if you are in a warm climate and it is doing it, that ain't normal.

Do you have an auto or manual? The manuals seem to want to idle up when you start a clutch release then stop. Could this be occuring when you start and then stop suddenly?

 

I'm in central Texas and it rarely gets below 30, but when it does the truck doesn't high idle. Tech said that is an option.
It is a manual and the idle seems to be sticking for no apparent reason. It is very random.

 

I would disagree with the tech on the 1000 rpm high idle. Just about every 3rd gen I have seen or heard about has this by default. He is probably mistaking it for the idle up option using the cruise buttons. Unless the temps are dropping under 30 degrees it won't activate the auto idle up feature.

You have the same problem a lot of others have reported with the manuals, they just periodically idle up to 1000 and hang there. To date I have not heard of a problem diagnosis or a fix, its just something that is there.

Some have reported if they engage the clutch part way the disengage it the idle will return to normal.

 

Will also do this if running too hot.Fill out your profile sig so we know what you drive and what state you live in.