My truck slowly started having 4wd problems towards the end of last winter, it used to take a couple try's after flipping the switch for the 4wd to engage, now it doesn't do anything. The light doesn't even come on when I flip the switch, bulb isn't burnt out. I tried swapping relays in the block, I have no clue which fuses to check because there's no label. I disconnected and cleaned the plugs on the T case shift motor, but now I'm stumped, any input would be great! Gotta love ESOF
2004 f350 4wd won't engage
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Good_ol_Boy
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Ideas anyone?
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Assuming you have electric 4x4 switch, have you tried putting it in neutral then disengage?
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Yeah, my 4wd doesn't work at all, there is no power to the transfer case, only 7v to the relay block, and no power at fuse 31
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Well I replaced the shift motor today, hoping that the sensor was interrupting the current, it's not. So basically it's narrowed down to wiring. Is there any common problem areas known for corroding on these trucks?
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143 Posts
Have you checked the vacuum lines? Mine wouldn't engage because of a disconnected line.
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This is a summary from the video “Vacuum Pump Motor Concerns on the Ford 6.0 F250-F350 Powerstroke Superduty.”
To test a vacuum pump, with key on disconnect vacuum line between passenger battery and passenger firewall, pump will come on. Plug pump back in and it’ll continue to run until vacuum maintained. If always runs, there’s a leak somewhere or pump weak. To test for pump weak, disconnect hose at pump and put your finger over it and start back up. It should shut off if not weak. If it is leaking, continue to go back from the lines to find which line is leaking. Each line should take a minute. The vacuum charged actuator is in the engine compartment above the passenger side wheel well. Looks like you can test the vacuum line before the actuator. I’m not sure how to test the actuator itself.
To test a vacuum pump, with key on disconnect vacuum line between passenger battery and passenger firewall, pump will come on. Plug pump back in and it’ll continue to run until vacuum maintained. If always runs, there’s a leak somewhere or pump weak. To test for pump weak, disconnect hose at pump and put your finger over it and start back up. It should shut off if not weak. If it is leaking, continue to go back from the lines to find which line is leaking. Each line should take a minute. The vacuum charged actuator is in the engine compartment above the passenger side wheel well. Looks like you can test the vacuum line before the actuator. I’m not sure how to test the actuator itself.
From a poster on ford-trucks.com
Fuse #'s only apply to 2002-2004
I'm assuming your 4WD isn't working, and that the 4x4 light on the dash is not coming on when you switch the switch to 4WD.
First thing to do is to check the make sure the 4x4 light is working. It should come on briefly when you start the truck. If it does then you know the light is working at least.
Find and check fuse #19, 27, 31, 33, 34, 45 and 111. Don't just visually inspect them, take them out and check them for continuity between the pins with a meter.
Get an assistant, get under the truck with a standard test light and find the 2 pin connector to the transfer case shift motor. Unplug that connector and connect the test light between the two pins of the connector. With the key in the RUN position (the engine doesn't actually have to be running), have your assistant turn the **** to 4WD. The test light should flash a number of times as the 4WD module tries to engage the shift motor.
IF the light flashes, then everything upstream of the shift motor is working. Inspect the connector, and the plug on the shift motor it connects to for any sort of corrosion or indication that there might be a bad connection. If everything looks good the shift motor is probably bad and needs replaced.
If the light does not flash then you need to find out why. The next most likely problem is one of the transfer case shift relays. The shift relays will be in a auxiliary relay box under the hood, drivers side towards the rear of the vehicle. They are usually in a relay box by themselves. Two identical relays with nothing else in the box. The box is wrapped from the factory with fabric electrical tape, but that might be gone if someone has already opened it. First thing to do is remove the relays and look for corrosion. If you find corrosion, clean it up good and try again. If that doesn't work, continue to the next step.
A good test of the relays is two remove them and swap their positions. One of the relays is used to turn the shift motor from the 2WD position, to the 4WD position, and then to the 4Low position. The other relay turns the motor back the opposite direction, from 4Low, back to 4WD, then back to 2WD.
When the relays are swapped, try shifting into 4WD again. If it works, you've found a bad relay and should probably just change them both.
If none of this works, then we'll need to look at the relay base wiring for corrosion and possibly move on to the 4WD control module.
Fuse #'s only apply to 2002-2004
I'm assuming your 4WD isn't working, and that the 4x4 light on the dash is not coming on when you switch the switch to 4WD.
First thing to do is to check the make sure the 4x4 light is working. It should come on briefly when you start the truck. If it does then you know the light is working at least.
Find and check fuse #19, 27, 31, 33, 34, 45 and 111. Don't just visually inspect them, take them out and check them for continuity between the pins with a meter.
Get an assistant, get under the truck with a standard test light and find the 2 pin connector to the transfer case shift motor. Unplug that connector and connect the test light between the two pins of the connector. With the key in the RUN position (the engine doesn't actually have to be running), have your assistant turn the **** to 4WD. The test light should flash a number of times as the 4WD module tries to engage the shift motor.
IF the light flashes, then everything upstream of the shift motor is working. Inspect the connector, and the plug on the shift motor it connects to for any sort of corrosion or indication that there might be a bad connection. If everything looks good the shift motor is probably bad and needs replaced.
If the light does not flash then you need to find out why. The next most likely problem is one of the transfer case shift relays. The shift relays will be in a auxiliary relay box under the hood, drivers side towards the rear of the vehicle. They are usually in a relay box by themselves. Two identical relays with nothing else in the box. The box is wrapped from the factory with fabric electrical tape, but that might be gone if someone has already opened it. First thing to do is remove the relays and look for corrosion. If you find corrosion, clean it up good and try again. If that doesn't work, continue to the next step.
A good test of the relays is two remove them and swap their positions. One of the relays is used to turn the shift motor from the 2WD position, to the 4WD position, and then to the 4Low position. The other relay turns the motor back the opposite direction, from 4Low, back to 4WD, then back to 2WD.
When the relays are swapped, try shifting into 4WD again. If it works, you've found a bad relay and should probably just change them both.
If none of this works, then we'll need to look at the relay base wiring for corrosion and possibly move on to the 4WD control module.
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Thanks, I actually already read that and started my search based on that with no luck. It is a great post though, and could be super helpful to a lot of people.
I have a feeling that my problem is from a rubbed through or corroded wire. I am losing power at the relays when I plug them in. I'm lost and frustrated.
I have a feeling that my problem is from a rubbed through or corroded wire. I am losing power at the relays when I plug them in. I'm lost and frustrated.
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