Swapped cruise control into my 2006 E350 with v10. Got a used steering wheel, brand new switches and clock spring from Ford. Had dealer turn on option. Cruise will occasionally activate, but when it does it immediately goes off. Nothing in my cluster illuminates (probably because its not factory option?). Switches do illuminate with the parking/headlamps. Before anyone asks, yes, all my brake lights work and I attempt to activate the cruise at speeds it should turn on.

I jumpered the harness from the pressure switch on the master cylinder to rule out a bad sensor, but nothing changes... My understanding is the PCM is reading this switch as normally closed. Unless its also reading resistance?

Pulled DTC's and there is two.
P0581 - Cruise Control Multi-Function Input A Circuit High
B1352 - Ignition key in circuit fault

Next step I can think of is opening the column to check the wiring.

Any other suggestions? Planning on taking a 4500 mile road trip in a couple weeks and would hate to have to do it again without the cruise working (yes, I did it last year without cruise control and it wasnt fun)

 

There is no cluster indication VSC is activated or engaged---that sucks but being an E-Series such things are all too common and aggravating.

Your issue could be the brake pedal canceling switch isn't adjusted properly---my own is set so closely a hard jolt can disengage it, simply hitting "resume" and its back on. There is adjustment of the switch which allows you to move it a bit further from the brake pedal arm. Not 100% sure this is your issue but with everything else you've done its highly possible.

HTH

 

I did take a glance at the brake pedal switch and noticed it was adjusted so slight movement of the pedal would activate the brake lights... I was going to disconnect the switch and take a drive to rule that part out... only to realize the van wont come out of park unless it senses the brake is engaged and that circuit is closed (duh moment). Although, I dont think the switch being adjusted wrong would give me the cruise control DTC im seeing, and my cruise control wont just come back on. I have to attempt to put it on 15 more times before I notice it works, and then within 1 second immediately goes off again.

Ordered a Ford helm repair manual and wiring diagram books off ebay, hoping it has the proper troubleshooting procedure for that code and im quickly able to pinpoint the issue that way.

 

I had similar problems on my 2003 E150, and after reading about the master cylinder switch problems, I ordered a brand new Motorcraft #SW-6350 cutout switch and harness kit (Ebay), and took out the old wiring harness (but left the old switch in the M/C because it wasn't leaking and I didn't want to break open the hydraulics) and just plugged in the new harness with new switch attached and zip-tied it to the radiator support and everything works perfectly again. Now, granted, I don't have the redundancy of a "third cutoff switch", but I figure with the brake light switch AND the steering wheel control switch, I didn't need ANOTHER back-up cutoff switch (and have never needed one in my older cars/trucks), plus, I totally removed the "fire hazard" factory setup. The harness and switch kit (SW-6350) is cheap on Ebay and maybe worth a try.
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So, here we are almost a year later. I hate when people do a drive by, post problems, then never return to share what they learned...

I finally got around to fixing this issue over the past few days using the Ford Service Manual I got on ebay for $100. I concentrated on the DTC P0581 that I was getting.

The pinpoint test for this DTC is prefaced with how the speed control system works... The PCM sends a signal through a light blue/black wire through the harness, through the clock spring, to the steering wheel switches. That signal is then returned to the PCM with the same path by a green/orange wire.

The first step was to disconnect the connector from the PCM which housed those wires. That wasnt exactly straight forward as two of the three PCM connectors were the same size. I found it to be the middle connector. I then had to turn the key on and the parking lights on.

With my DVM, I had to check each wire for voltage, checking if either wire was shorted to power. I got no voltage.

Next it told me to turn the lights off, turn the key off, and check to see if either wire had resistance with ground (basically continuity with ground to see if the wire was grounded somewhere), The wires were fine.

Next it asked me to check resistance value between those two circuits which was out of spec. Then asked me to disconnect a connector under the column which goes to the clock spring and check for continuity between the aforementioned wires. Continuity was fine.

Then it asked me to check resistance of the clockspring. This is where things got tricky. It asked me to remove the airbag, which I basically just unbolted and set off to the side a little. Unplugged the steering wheel switches and and it asked me to check resistance between the "pin 4" of the bottom connector and "pin 1" of the clock spring connector, and "pin 2"/"pin 2"... It asked if resistance between either of those circuits was less than 5 ohms. I got 6 ohms on my Fluke 88V (not a cheap meter).

If I had followed the manual it advised to install a new clock spring. But the clock spring and switches were both new.. Although I got the clock spring new from Ford.. the switches were new but from amazon. I decided to test my meter by checking resistance without anything inbetween... Basically just the leads. I got 2 ohms from just the leads. So I figured that my clock spring readings were really 4 ohms, which the manual directed me to replace the switches.

I decided to replace the switches.

Switches replaced, cruise control works perfect.

Factory service manual was key in diagnosing this issue. Dont be a parts changer!