4x4 Low wire

[Eaglefreek]

I've got a 99 E350 that is 2wd. While checking the oil the other day, I noticed an orange wire with a label with "4x4 Low" on it. It's a passenger van with a high top and was a wheel chair shuttle. Just for curiosities sake, I'm curious what the wire is for.

 

[tgreening]

My extremely uninformed opinion would be that its wiring related to the 4x4 Low light that's usually on the dash somewhere for 4x4 equipped vehicles. My guess is the wiring harness is generic and the wiring is there for the light, even if the actual hardware is not.

 

[Eaglefreek]

I didn't turn up a whole lot on my research, but I noticed 2 more wires labeled CTO and PTO. CTO is clean tach output and PTO is for power take off. My best guess is the 4X4 Low wire probably gets grounded when in low so the PCM can modify transmission shift points.

 

[Herbie]

Here's a second guess for "Generic Wiring Harness".

On the Chevy's, we get something similar. The wiring harness is unique, but the main ECU, transmission computer, etc. is shared between Astro and Blazers. If you swap the Astro transfer case from AWD to a PT 4WD with a Low-range, the ECU freaks out when the revs don't match the output speed. It'll limit the revs and hold you in 1st or 2nd gear. However, if you add a wire to the correct pin on the ECU, and ground it when in 4LO, the "Blazer" part of the ECU knows what to do and the ECU is happy.

Thanks general!

 

[nely]

I didn't turn up a whole lot on my research, but I noticed 2 more wires labeled CTO and PTO. CTO is clean tach output and PTO is for power take off. My best guess is the 4X4 Low wire probably gets grounded when in low so the PCM can modify transmission shift points.

I believe you are correct about the 4x4 low wire. The superdutys have it as an input to the pcm when in low gear.