I have a 2002 F-350 SRW CC SB. My ESOF isn't working. No 4X4 light on the dash. Light is good as it lights up when the truck is started. I pulled the codes and got the following.

P1866 - Transmission Transfer case system concern.
C1728 - Unable to Transition between 4H and 2H
p1876 - Transfer Case 2-Wheel Drive Solenoid Circuit Open Or Short To Ground

I changed the vacuum solinoid on the passanger side fender.
I changed the two relays on drivers side.
I changed the transfer case shift motor.

When changing the shift motor I have to move the shaft in the transfer case to line up with the new shift motor. I believe this put the transfer case in 4X4.

Now the 4X4 light on the dash is on and will not go out. It will not shift into 4X4 Low as well.

I wonder if it is the switch on the dash? I pulled the switch out and it has four pins. I would think one for power and one for each position of the switch. I rang the switch and only get continuity between the two outer pins.

Does anyone have a wiring diagram of the ESOF system?

I will go pull the code again and report back with what I find.

 

Pins 1 & 4 on the switch assembly are for the light bulb.

Pins 2 & 3 are the switch for the selector. Each of the 3 switch positions has a different value resistor in series so you you will need to up the range on your ohmmeter in order to measure them, they won't show simple continuity. I haven't looked up the values, but I'd expect the three to range between 500 and 10,000 ohms.

 

Thanks for the quick reply. I check the resistance between pins 2 & 3.

Here's what I got:

Selector in 2WD - Open
Selector in 4x4 High - Open
Selector in 4x4 Low - 392 ohms.

Sounds like I need a new switch.

 

Should be:

4L - 340-380
4H - 1050-1150
2WD - 3.7K -4.1K

Make sure you do not have the ohmmeter on too low of range. If you do, the higher resistances will be erroneously measured as open.

 

Thanks for the info. I was using a auto range meter. I got out the Fluke 8062A meter and got

4l - 360
4H - 1100
2WD - 3.9K

So it looks like the switch is fine. Now what?

 

Haven't seen any replies lately. Anyone have any suggestions of what to check now that I have replaced the vacuum solenoid, Relay's, and transfer case motor and checked the dash switch. Also all codes I was getting are now clear.

 

I had this problem with my 94 Ranger. To truly "fix" the problem, I swapped in the mechanical shift transfer case. That lever never gives me any issues. When my ESOF becomes a problem in my F250, I will probably go the same route. I already have the regular hubs (non-vacuum units).

I would pull the motor off the transfer case and turn the **** to see if it even moves. You will need a jumper to go from the motor housing to the t-case to complete the ground.

If the motor moves, I would assume there is binding the transfer case. This could be caused by the vacuum actuated front hubs being stuck or seized in the locked position. You said you put the new motor on with the t-case in 4x4. If the hubs were seized and you drove on pavement, that could be an issue. Put the truck on jack stands to relieve and pressure on the 4x4 system. You could also drain and replace the fluid to see if you get any metal shavings out.

If the motor does not move, I would run a ground from the motor housing to the battery. If it works, then there is a grounding issue somewhere. If it doesn't work, we will have to think of something else.

 

I'm going through this with mine right now. Except mine's an 04, a bit different. Have you checked for power at the connector (2 prong) at the Tcase? Also have you checked all the fuses? Like actually pulled them out and tested? Your problem could also be the GEM as well. IIRC the 02's GEM is under the dash on the drivers side, and these trucks have been known for having problems with their windshield seals. If you've had leaking problems I'd check there and pop it open and look for corrosion.

 

Thanks for you input anyway

 

Never had a leaking problem. I am going to check for power on the relays and them the motor connector once it warms up some. Truck is in 4WD now and I have the hubs locked manually. It not my daily driver so I can live with it until the weather warms up here. It was below 0 here today. I didn't any help when I was working on it last so I couldn't check voltages while moving the dash switch.

 

I finally got time to work on this today and thought I would give an update. I got a copy of the wiring diagram and checked a few things out. In the wiring diagram I checked pins 86 on both relays and had power. I then checked continuity from pin 30 on both relays these are the wires which run the motor. I got OL on the meter which is an open circuit. I then checked continuity on each of the wires and the orange wire was open and the yellow wire was OK. I was just going to replace the harness so I started to put the wires back into the loom. When I got near the front of the loom where wires go from the loom to a hard plastic cover I thought I would check the orange and yellow wires. I pulled on the orange wire and it came right apart. I checked the yellow and it was till one piece but it to was damaged. I cut a short section of each out and soldered in new wire and double shrink wrapped them. I then taped up everything and wire tied the harness back in place.

My ESOF now works from the dash switch. Hubs are still not locking in but that's something for another day.

I have another set of locking hubs to put on and I will check for vacuum leaks.

So I guess I have a spare transfer case motor and relays now.

Also when I put it up on the ramp and engaged the e-brake the e-brake cable broke. So I ordered a new parts.

I was going to attach a photo of the wiring diagram but I guess I don't have enough post to add photo's