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High Idle doesn't engage (not wiring issue)

Matt Bachand

Matt Bachand

Depends on the 6.5
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Worcester, MA
I assumed it was wiring. I Checked first the switch, then manually doing switches job with wire ends no engage,

Pulled computer, pins look fine. Installed temp wire connecting the 2 (for highest idle) and nothing....

Tried in neutral, parking brake, park...

Any reason the computer would disable this as if it were in drive???

Stored code?!? (wouldn't make sense but maybe?)

Thanks. Necssity for winter time IMO... must fix.
 
Maybe some safety interlock???

I have read some deactivate when a clutch is pushed in. I imagine it can't be set on when in "drive mode". Maybe check cruise control is off, brake pedal is coming back all the way up, and throttle too. Not sure what else would make the ECM think the truck is being driven or in drive????
 
bison said:
was it working before, Or is it a new install ?.
Brake switch maybe?
Click to expand...

It stopped working all of a sudden out of the blue a few months back. I just assumed it was wiring and figured I'd get to it before winter.

It goes off when put in gear. Does it go off when foot is on brake?
 
Matt Bachand said:
It stopped working all of a sudden out of the blue a few months back. I just assumed it was wiring and figured I'd get to it before winter.

It goes off when put in gear. Does it go off when foot is on brake?
Click to expand...

From what I've read some go off when brake is applied or it is put in gear, FWIW mine stays on when in gear or brake applied.

Leo
 
So OBD1's stay on, OBD2's go off in park or brake applied...........


Now if my brake switch was out, wouldn't my apply brake to shift out of park and brake lights not work?

And the neutral safety switch or PRNDL Lever would apply to my starter not cranking?

Both of those systems seem fine.
 
Last edited:
Your brake switch has 3 sides to it, one for the brake lights, one for the ABS and PCM, and then one for the shift interlock side. Try pulling the brake pedal towards you and see if it will engage.
 
THEFERMANATOR said:
Your brake switch has 3 sides to it, one for the brake lights, one for the ABS and PCM, and then one for the shift interlock side. Try pulling the brake pedal towards you and see if it will engage.
Click to expand...

Did not engage. I will test it out more in overdrive lightly press the pedal to see if PCM puts the tranny in coast mode.

Interesting thing though, I did unplug all my ABS stuff a few months back...

I have no light on, But I removed 3 sensors out of the unit. I will try hooking them back up and seeing if it makes a difference.
 
I need someone to try something for me, or perhaps you just know.

I seem to remember driving in 3rd and highway speed, and when I hit the brake pedal, the tranny 'freewheels' where rpm drops to idle. I remember this, because I was thinking when applying the brake, its losing its engine braking.

However, my truck no longer does this.

Can someone verify OBD2 that this happens. Thanks.
 
Brooklyn Tow said:
Works like that on my rig.
Click to expand...

Thanks Louis.

So now I'm suspecting brake switch. It is not communicating with the PCM, thus the high idle is shut down, and its not 'freewheeling' for lack of better word when i tap it on the highway.

I assume this is on the brake pedal? I will try cleaning it up.
 
Schwind said:
Just a thought. You stated earlier that you had unplugged part of the ABS system. I wonder if that is what is producing the problems you are having?
Click to expand...

I re-hooked it up, and high idle still didn't work. Havn't road tripped it to test the brake thing though.

IIRC I disabled the abs around may and high idle gave way a few months later.

I should double check my brake lights working, although I was tailed by a few cops in recent driving, i'm sure they'd pull me over if not brake lights... perhaps they were just in awe of the nice rig!
 
I think I see it up there tucked way high on the brake pedal that goes into the master cylinder...

ITs all wet :(.... I have a leaky going on on the brake system master cylinder area, Its apparent outside, as well as inside the cab.

Looks like a real pain to remove and clean up...
 
Matt Bachand said:
http://www.rockauto.com/catalog/x,carcode,1053425,parttype,10474

Why so many options here? How many brake switches are under there?

One actually says TCC in the detail.??
Click to expand...

There is only ONE switch, the others are connectors if I read it correct, cauz if I click on the link, the page shows up in german language.

What about this :

http://www.lmctruck.com/icatalog/cd/full.aspx?Page=29
0029.jpg





Cu,
Sven
 
Thanks Sven. Cheap money too.

I'm going to get up there and clean it out and see what happens.

I want to wipe clean this fluid while I'm there and find out where/why my brake system is leaking........................ Never get ahead... I guess I see why people buy new, although I wouldn't even think about it. I've bought new before and things leaked... just dealer fixes them, huge hassle all the same.
 
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