4x4 Not Engaging | Ford Explorer Forums - Serious Explorations

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4x4 Not Engaging

T.J. Boismier

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Joined
September 13, 2018
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City, State
Texas
Year, Model & Trim Level
98 XLT
I have a 98 Explorer XLT with 4x4. When you turn the switch to 4HI, the light on the dash comes on saying 4HI. When you turn from 4HI to 4LO, the 4HI light stays on. When you turn from Auto to 4LO without pausing at the 4HI, no lights come on. The 4x4 doesn't work throughout the whole thing. I did check the fuses and they were fine, I pulled the switch off the dash and took it apart and there was no corrosion. The transfer case was rebuilt 50k ago, and the 4x4 worked 20k ago, but it sat for a year and I revived it just last month and only put a few miles on it.
 



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Put the truck in neutral then select 4lo and put it back into gear. You should now have 4lo engaged.
 






Will try that later. If that helps, 4HI still doesn't turn the front wheels.
 






Still does not go into 4HI or 4LO even going into 4wd from neutral. Help?
 






This is where you need to search the forum. There are plenty of threads that deal with troubleshooting the 4x4 system.

Edit: You never said if the auto 4x4 works.
 






One more thing worth reiterating...it's crucial that you run the same size, style and tread depth tires on all four wheels or else you will eventually damage the transfer case. If you've not been doing this since it was rebuilt, it could be the problem.
 






All four tires have been changed at the same time for the life of the vehicle.
 






Can anyone tell me how to hotwire the switch or something along those lines to make sure that the switch is the problem before I order a new one?
 












I have attached a circuit diagram. On the lower right you will see the switch, and that it has 3 different resistors in series on each of the three selections possible.

You can either put the switch in each position and use a multimeter to measure for "roughly" that resistance, or you can jumper across the white/light-blue and the gray/red wires to it with a resistor you supply yourself, while the switch is disconnected, to see if that engages the front wheels.

However I would probably start troubleshooting this by having a multimeter hooked up to the brown wire going to the "magnetic clutch control" to see if it is getting 12V (relative to chassis ground) when the switch is in 4Hi or 4Low. That brown wire sends power to the transfer case to engage the front wheels through an electromagnetic clutch coil as seen at the very bottom of the diagram.

Since you aren't getting 4Hi you don't really need to worry about 4low yet.

If you are getting 12V on that brown wire (which can also be accessed at the shift control module to the left of the radio in the dash, you don't have to crawl under the vehicle to get to the upstream portion of that wire run) then you have either an electrical issue down at the transfer case, or at the coil in the case, or something mechanical.

If you aren't getting 12V on that wire, it is time to trace the circuit backwards from that point. Instead of elaborating on that further now, it would be good to know which way you need to trace this further depending on whether there is 12V on the brown wire in 4hi.
 

Attachments

  • transmissions-4wd-circuit-1-of-1.pdf
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Okay thanks for the info. Will try that later.

Does it have to be a resistor, or can I do what I do with tractors and the like when I'm confirming a bad switch and take a piece of wire, strip the ends, and insert the bare wire into the terminal?

Also, I'm pretty sure it is the switch, because the other day I was driving around with the switch in 4 lo and the light on the dash came on, so I went into a field and floored it and all four tires were loose and spinning. Could be the switch is just finicky. After a while the light went off and it was back in 2wd.

Edit: Also, I see the anti lock brakes on that diagram, the abs light has been on for a while and I never really cared. Could they be related?
 






^ No you can't test that 4WD mode switch by just using a jumper wire, because it doesn't directly switch the power to the powered clutch, nor just a relay, instead is an analog logic signal to the GEM module, but you don't need a resistor if you just measure resistance between the switch contacts (per each switch position) with a multimeter instead.

You could test whether 4WD engages by using a jumper wire between the battery and the brown wire to the Magnetic Clutch Coil, then if that works you at least know it's electrical before it gets to the clutch coil.
 






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