no low range 4x4
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no low range 4x4
2000 6.8 v10 F250 supper duty crew cab.
4x4 high switch's on/engages ( manual lock hubs installed) but 4x4 low will not engage.
Brake input/out put tested good. Trans switch Park/"N" both test good.
P.c.m. reads switch output in all modes, ( dash 4x4 selector)
Motor on T case locks in 4x4 high, have not tested power otherwise.
Solenoid on fender has power, have not back probed to test solenoid value.
All fuses @ left lower dash and under hood have tested power on both legs.
Located 2w to 4wh 4wh to 4wl relays on driver side next to main junction fuse location and swapped relays with no change.
Next step Im looking at is geting a set of back-probes from my matco guy tomorrow and back probe the " solenoid" on the right fender.
Missing anything!?
4x4 high switch's on/engages ( manual lock hubs installed) but 4x4 low will not engage.
Brake input/out put tested good. Trans switch Park/"N" both test good.
P.c.m. reads switch output in all modes, ( dash 4x4 selector)
Motor on T case locks in 4x4 high, have not tested power otherwise.
Solenoid on fender has power, have not back probed to test solenoid value.
All fuses @ left lower dash and under hood have tested power on both legs.
Located 2w to 4wh 4wh to 4wl relays on driver side next to main junction fuse location and swapped relays with no change.
Next step Im looking at is geting a set of back-probes from my matco guy tomorrow and back probe the " solenoid" on the right fender.
Missing anything!?
Senior User
Joined: Feb 2004
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From: Tennessee
Dave, found this from another site. He has a 99 SD with a GEM module. Don't know if your 2000 still had the GEM or not, but if it does this info may help you.
Ford Truck World - Transfer case/ESOF problems (Super Duty)
Ford Truck World - Transfer case/ESOF problems (Super Duty)
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Joined: Jul 2002
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From: Long Island USA
The only thing I am aware of that would keep LOW from engaging is brake signal and Park/Neutral signal.
Check the switch just for the heck of it - make sure it's doing it's thing in the LOW position. It's a resistor. One resistance for HI, a different one for LOW.
If this is all working, AND you are getting these signals at the GEM pins (important to check) then it sounds like the GEM is bad.
Check the switch just for the heck of it - make sure it's doing it's thing in the LOW position. It's a resistor. One resistance for HI, a different one for LOW.
If this is all working, AND you are getting these signals at the GEM pins (important to check) then it sounds like the GEM is bad.
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[QUOTE=Krewat;15191355]
Check the switch just for the heck of it - make sure it's doing it's thing in the LOW position. It's a resistor. One resistance for HI, a different one for LOW.
Dumb question...If the pcm sees the switch working is it possible its working in the wrong range of ohms? Snap on modis sees out put on the switch in the low position.
I got the probes today. Have diagram from shop key, going to test signal at the motor with some one moving the switch in cab, and go back from there.
I am starting to really appreciate the floor shift T case in my old str8 6
Check the switch just for the heck of it - make sure it's doing it's thing in the LOW position. It's a resistor. One resistance for HI, a different one for LOW.
Dumb question...If the pcm sees the switch working is it possible its working in the wrong range of ohms? Snap on modis sees out put on the switch in the low position.
I got the probes today. Have diagram from shop key, going to test signal at the motor with some one moving the switch in cab, and go back from there.
I am starting to really appreciate the floor shift T case in my old str8 6
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New User
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Dave, found this from another site. He has a 99 SD with a GEM module. Don't know if your 2000 still had the GEM or not, but if it does this info may help you.
Ford Truck World - Transfer case/ESOF problems (Super Duty)
Ford Truck World - Transfer case/ESOF problems (Super Duty)
Yes It has a GEM located on the lower left, just behind the in cab fuse block.
Gem uses inputs/out puts to control various body/chassis components. If the PCM verify's the circuit at the switch out put through the gem should I still look at the Gem Mod,? Is there a test via a scan tool such as modis, maxme to run on the GEM?
Senior User
Joined: Feb 2004
Posts: 154
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From: Tennessee
I would think there is an actual dealer type test tool for the module but I don't know. Have you pulled the shift motor from the transfer case to see if it does change from HI to LOW position outside the T-case? I have read where sometimes the motor will get all the right signals, but just does not have enough power to shift the case. Here is another thread I found with that problem:
https://www.ford-trucks.com/forums/8...-fly-help.html
https://www.ford-trucks.com/forums/8...-fly-help.html
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Thanks I will take a few min to test that. Might be the switching side of the motor. That would make sense why it would work in high but not low...would be great if that's it, among the big components in this circuit the actual servo motor is prob the cheapest.
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From: Long Island USA
The motor itself only runs in two directions. It runs from 4x2HI into 4x4HI and because the GEM says so, it stops. Then when you command 4x4LOW, it continues running the motor in the same direction. In other words, if it goes from 4x2 into 4x4HI, then the motor works well enough to go into 4x4LOW, IF the GEM tells it to.
Does the dash 4x4 light go on when it gets into 4x4HI?
Does the dash 4x4 light go on when it gets into 4x4HI?
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I have a power probe and got a set of back probe pins, I don't want to take the pigtail off the contact plate or the motor, due to the age of the connectors and the fact that I already had to replace the range sensor pigtail on the transmission due to the prev owner snapping the locking clip off and ziptieing it. I gusse I will have to bypass the GEM or find the pin to test on it. IS there a floor shift kit for the Tcase? lol
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OK so using a Relay bypass switch, supplying power at the 2h to 4h relay engages, and the 4h to 4l also engages, motor executes as it should with no issues, so the issue is now isolated to the Circuit from the G E M to the Shift relay's.
It is sooooo fun Diagnossing Electrical issues with limited time, and no shop!! lol ( we are not allowed to work on personall stuff at work )
It is sooooo fun Diagnossing Electrical issues with limited time, and no shop!! lol ( we are not allowed to work on personall stuff at work )
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