Question Cruise and high idle do not work and I don't have a cab brake light

[rjglenn]

It's a 2005 F350, it is a cab & chassis 4x4 standard diesel It does not have, nor has it ever had the third stop light up on the cab. I don't know what this truck was in it's former life, where the third light would normally be there is a piece of black plastic. Maybe it used to be a box truck, but now it's a flat bed.

Now that we have chased that rabbit around, here's my question. My cruise control does not work at all. It has a cruise control steering wheel, the backlights for the buttons work and the horn works, but no cruise. Lots of places on the net discuss a test mode, but that doesn't seem to work either.

Applying 12 VDC to the purple/green wire in the acc bundle does not result in a high idle either. Apparently one of the qualifiers is that the brake lights must be working. The brake lights do work, except for not having the stop light.

Anyone have a similar experience or any ideas.

 

[BIG JOE]

CC not working:

There's a VSS (Vehicle Speed Sensor) on the top of the rear Dif.. remove and clean it.. better yet.. replace it*.

High Idle:

Is it OEM ? or Aftermarket ??

*The VSS [may] have something to do with the High Idle not working too ?

Joe

 

[rjglenn]

Thanks for your quick reply.

Kind of doubt it is the VSS, the speedometer works as well as the anti-lock brakes.

High idle is neither OEM or aftermarket, it's not a thing, it's a condition. It is a matter of applying voltage to a particular wire underneath the dash. For the high idle to work there are certain criteria - the truck must be in neutral, the parking brake must be applied, the brake lights have to work, and +12 VDC has to be applied to a wire that is in a marked bundle behind the fuse panel. I found the bundle, I found the wire, I applied voltage, I met the conditions (I thought), but no joy. Since the brake lights also have to work for the cruise control to work I'm seeing a pattern. I'm assuming that the missing third brake light is the culprit and I am asking if anyone has dealt with this before so I don't have to reinvent the wheel. Where do I find the wire for the third light so I can trick the PCM?

 

[DaveBen]

The High Idle is in my truck. Check my photos and you will see what goes where. It is really simple as you said.

Dave

 

[DaveBen]

Sorry my pictures don't show now that wedshots screwed with their format. I will try to dig them up. I will look under my dash tomorrow.

Dave

 

[BIG JOE]

Thanks for your quick reply.

Kind of doubt it is the VSS, the speedometer works as well as the anti-lock brakes.

High idle is neither OEM or aftermarket, it's not a thing, it's a condition. It is a matter of applying voltage to a particular wire underneath the dash. For the high idle to work there are certain criteria - the truck must be in neutral, the parking brake must be applied, the brake lights have to work, and +12 VDC has to be applied to a wire that is in a marked bundle behind the fuse panel. I found the bundle, I found the wire, I applied voltage, I met the conditions (I thought), but no joy. Since the brake lights also have to work for the cruise control to work I'm seeing a pattern. I'm assuming that the missing third brake light is the culprit and I am asking if anyone has dealt with this before so I don't have to reinvent the wheel. Where do I find the wire for the third light so I can trick the PCM?

Check the brake pedal brake light switch ?

Check the pressure switch on the master cylinder ?

 

[rjglenn]

The brake lights work so I'm sure the pedal switch is good, unless there is more to that switch than it appears. I replaced the switch on the master cylinder awhile back with no change.

 

[BIG JOE]

There is, or can be a bit more Whizo stuff to the brake switch. Yours being a C & C.. and not being sure what the spec package is/was but it does have cruise.

It's been my experience that these F series can come with Generic wiring harnesses.. (On my 012 Lariat I've noticed a number of unused plugs, and such.. that I'm assuming are for King Ranch Bells'n Whistles.)

There could very well be a 3rd brake light wire & plug.. just not connected, behind that plate.

Have you checked that out ??

As for High Idle ? Maybe a "Duh" to you but theres good number of temp sensors.. on the engine that are PCM critical, for the High Idle to come on-line.

Joe

 

[rjglenn]

I'll have to pull the headliner to get to the screws that hold the plate so I can take it off to see what's there. I looked at the brake light switch, you're right. Its no simple two wire circuit, but instead a bundle of wires. I'll work on the plate and then go from there. Seems like this is much more complicated than it needs to be.

 

[BIG JOE]

I'll have to pull the headliner to get to the screws that hold the plate so I can take it off to see what's there. I looked at the brake light switch, you're right. Its no simple two wire circuit, but instead a bundle of wires. I'll work on the plate and then go from there. [Seems like this is much more complicated than it needs to be.]

I hear ya ! Waaay over complicated, IMO too.

Yours being a 350.. if it has Cab lights.. I'd betcha it has the 3rd brake light wiring too.

One easy check you might make.. There should be an *Ambeint Air Temp sensor on the Air Filter Box or snorkle.. IF IT senses Coooold intake air.. it trips the PCM to go to high idle.. then the other sencors.. like Oil/Coolant temp, and the like, are the ones that trip it off when Op temps reach X.

Sometimes the sensor tip gets fouled.. or the connector gets dirty ?

All the batterys, cables, clamps and fuses good ?

Joe

*I'm an X 7.3 guy.. so maybe some of the 6.0 guyz will jump in here and keep me in line ??