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James, Ford Technician
Category: Ford
Satisfied Customers: 3628
Experience:  Ford Senior Master Tech, Ford gas and diesel expert, ASE Certified
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Ford F250: 2001 Ford F250...*****does not enguage

Customer Question

2001 Ford F250...*****does not enguage ...light comes on upon start up.. does not when 4wd switch is turned on.... vacuum pump works... runs...cuts off indicating no leak...
in cab switch... has no continuinty ...
changed switch... has continuinty on outside two poles.. still no light or 4wd operation
vacuum switch has 12 v on two poles in 2 wheel ... then 12 v on the other ( ground reversed ??)
Submitted: 2 years ago.
Category: Ford
Expert:  James replied 2 years ago.
Hello and thanks for choosing just answer. On your vehicle do you have a smaller fuse panel under the steering wheel or a large one. If you have the large one it will be almost 18" long. If you could let me know which one you have it will make it easier to assist you.
Customer: replied 2 years ago.
believe it is a a smaller one.. have checked continuinty in all fuses under dash and under hood... not relayshave been working while waiting for you... have no voltage at electric motor in transfer case... what supplies this motor
Expert:  James replied 2 years ago.
Here are the wire diagrams. The*****is controlled through the gem module. This is mounted on the back side of the fuse panel inside the vehicle. If the light illuminate I would start and idle the vehicle. Turn the switch selector into 4wheel drive and smack the fuse panel with a flat Palm. If the gem module malfunctions this is very common. This is most likely what you are going to find why the*****isn't working correctly.
Customer: replied 2 years ago.
If the light illuminate .....what does this mean?the 4 wd light and the low range light come on when the vehicle starts.... then goes out ... telling me that the bulbs are good.the lights never come on after that.If I smack the fuse panel and the system starts working ... do I just leave alone.?..If it does not work ... do I replace the GEM module?
Expert:  James replied 2 years ago.
When the lights come on it does indicate the bulbs are good and the system isn't disabled. If you smack the gem and it works then the ground driver in the gem module is likely bad. If smacking it doesn't work it still can be the gem module. Do you have a scan tool that can test for codes in the gem module?
Customer: replied 2 years ago.
Customer: replied 2 years ago.
could take to Auto Zone tomorrow.
Expert:  James replied 2 years ago.
Autozone won't be able to read codes in a gem module. Did smacking it make a difference?
Customer: replied 2 years ago.
am in South Texas... tornado warning.... heavy rain.. dark... millions of mosquitoes... will try tomorrow.
Expert:  James replied 2 years ago.
Sounds good?
Customer: replied 2 years ago.
Internet was down due to storm. Smacked several times... no difference... pulled fuse to reset gem... no difference.. what's next?
Expert:  James replied 2 years ago.
If you are getting power to the transfer case shift motor on the two large wires when shifting I would still suspecr the gem module is faulty.
Customer: replied 2 years ago.
I do not have power to the transfer case. I also suspect the gem module. where can I get the codes read for the gem module?
Expert:  James replied 2 years ago.
In order to test gem module codes a basic code reader won't do. You will need on that can test different modules. There prices vary but usually $300 will get you a basic one.