So if I remember correctly you have to have the truck in neutral with the parking brake on for the manual trucks anyway for a certain amount of time for your high idle to kick in. Well, mine has never worked. I also heard if I remember correctly the brake warning has to be on on the dash for your high idle to engage. If that is the case that's my problem. I have a fault code for brake light warning output failure and my brake warning light has never worked. So my question is, if the indicator bulb for the e-brake does not work can it stop my hi idle from kicking in? Thanks!

 

I'm pretty sure the IAT sensor has to register a low enough ambient air temp to necessitate the high idle.

Edit: Unless you have a tuner w/ that option of course.

 

Yes, the "parking brake" light must be functional in order for the "high idle" to kick in on the ZF6 trucks.

A failed bulb (if that is the issue) could likely stop the high idle from starting. Although, be 100% sure the little switch under the dash (parking brake switch) is making good contact and is functioning properly. I used a modified version of the Y2KW57 fix for the POS switch on the pedal mechanism.

 

To your point, please see the snip from the PC/ED volume of the Ford Service Manual.



Also...



Based on some very, very light further research. The auto truck must be in park and the manual truck must have the parking brake light ON. In addition, the high idle is activated by the PCM based on the input data from the EOT and IAT sensors. For the ZF6 truck, the service brake or the clutch being applied will cancel the high idle if I remember correctly.

So, any one of the criteria above not being met will not allow the high idle to kick in.

Lastly, it takes a couple moments for the high idle to kick in. It does not start to high idle immediately after the engine has started.

 

It's got to be pretty cold for it to kick in. I also think the ebp sensor has to be reading correctly. When my ebp tube got stopped up the factory high idle and ebpv quit working until I replaced the tube.

 

Likely the little switch where the parking brake pedal is.
EOT sensor is the other thing your year truck will use to determine if high idle is needed.

 

So if oil temp is above 122 then no high idle regardless of ambient temps. Interesting, I'll file that one with the rest of the strange facts and nearly useless trivia that rattles around in my hat rack. Never know when that nearly useless trivia is the difference between getting home or calling for help. Any idea what IAT threshold is?

 

The only details I could find during a quick look were... I'll look a bit more for IAT input range in conjunction with the high idle more later.

 

The little switch on the parking brake completes the ground to the dash light. Mine was corroded pretty bad and the light wouldn't come on but a new switch was only a few dollars (in 2009) so I changed it and my high idle started to work, although it's rarely cold enough here to activate. Works good when we travel in the high mountains in Winter though.

 

What is this @Y2KW57 fix?

 

Parking Brake Pedal Pin Switch Fix

Parking Brake Pedal Pin Switch Fix in different thread

 

My version of the mod is identical to his, except I wrapped a piece of uncoated copper 24 gauge wire between the contact posts and the plate in the red circled area below. This way, there is a bit more height on the contact posts for the plate to make a connection. I did this 6+ years ago and it is still working as intended.

 

You'll be hard-pressed to get the automatic high idle to work in your neck of the woods.

There are a few criteria to be met that allow the function to work.

Intake air temperature, oil temperature, parking brake, idle time, and even a PCM that has the function programmed into the calibration.

Unless you're seeing <40-ish degree mornings, it'll never come on.

 

Okay so I read what everybody said. Everybody makes good points and I appreciate everybody tuning in.

So my cousin has the same truck I do but his is a 350 srw, has an automatic transmission and a flatbed. I think he just passed 120k miles on it. He just bought it not long ago. it's in good shape with low miles. I just got done putting a mishimoto upgraded transmission cooler in for him a couple of months ago. It's also funny because the truck I have now is the truck he used to have so it's funny for the previous owner to see what the truck looks like now after everything I've done to it. Also seeing my before and afters, somehow he thinks I know what I'm doing so he has me do some work on his truck. Actually this weekend I'm doing an oil change on that truck, his other work truck, and some other mechanical things around the shop that need to be fixed and maintenance done on etc etc. Anyway....

i was at work with him the other day and I was there before everybody hooking up to the trailer and the truck engaged in high idle. We've had a cold front come through this week and it has gotten pretty chilly. But the reason I know my high idle doesn't work is because a couple years ago when I first bought the truck, I would let the truck idle in the yard for 10 to 15 minutes before I left because it was 13° outside so I wanted to let her idle for a little longer. I tried to get high idle to work a few times but it never would. I know how the stupid little crappy button works. I know that everything with the wiring is good because forescan actually has a PID for the brake just like on the dash. I put that pid on my atoto and checked it with the pedal and sure enough when I push the parking brake pedal in it says brake on when I release the brake it says brake off. So the wiring and all at least to the PCM works. Assuming it goes to the PCM at all that is. the ground could go directly to the gauge cluster to the bulb but I'm not too sure. Maybe it does go to the PCM and that's how my forescan is able to show that pid? I would think it would have to go through the PCM in some way so that the truck knows when to high idle. Who knows?

So to the best of my knowledge, my best course of action next would be to check the bulb on the dash. If that is good then I have a wiring issue somewhere. The other thing I also noticed is when I first turn the key on and every light on the dash is supposed to come on, the parking brake light never does. But using forescan I know that at least the wiring says the brake is on.

I have also inspected the pedal switch and wiring as best I could without spending too much time on it, I couldn't find anything wrong anywhere.

I will get around to pulling the gauge cluster and checking that bulb. Also the other question, I replaced a lot of the bulbs in the dash with LEDs. Well at least the important ones. The ones that actually light the cluster up and the low fuel light and stuff like that I put LEDs. For the brake light i'm probably going to put another incandescent bulb in. Does anybody else have any issues with their LED's? I feel like the LEDs are too bright and they bleed through from one spot to another. Like when you turn on the main illumination it will light up the lights around the tachometer that are not supposed to be on. Albeit very dimly. It's not a problem at all,I just don't like how the water in fuel light and what not will light up a little bit when I turn on the main illumination. I can still very easily and clearly tell when those lights are actually on or off. There's just a little bit of bleed through from the main illumination LEDs. Thanks everyone!

 

For the sake of reason, just get a hydra and load a hi idle tune on it