Auto 4x4 Out
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Freshman User
Joined: Jul 2012
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Auto 4x4 Out
At first my truck would try and engage the auto 4x4 but now the only thing that happens is the light comes on the dash and nothing else. I've checked the vacuum lines, checked the hubs for leaks and checked the vacuum pump. All seems OK. The light comes on in the dash but not engaging. Someone suggested I need a new computer for what I assume is the transfer case under the dash and that the only way to get one was through the dealership since they needed to be programed. Has anyone run into this issue at all?
It's a Van Gogh
Joined: Feb 2010
Posts: 7,812
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From: Elk Grove, CA
O yeah. ESOF diagnostics can be complicated but a new computer is almost never the answer. Let's start at the beginning; can your HVAC switch to anything other than defrost when the ESOF switch is engaged? Could be a bad transfer case motor or related fuses/relays/wires too.
Here's a great thread with lots of info. Even with the "there's always another day"...
Here's a great thread with lots of info. Even with the "there's always another day"...
Senior User
Joined: Aug 2010
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From: Princeton, MN
what year is it? they changed the system a bit through the years.
does it work if you manually lock the hubs? if yes then its an issue with the hubs/vacuum setup. If not then it's another can of worms.
If the light on the dash is on its because the truck thinks the Tcase is in 4x4, if it isnt then theres a 4x4 control module above the glove box that can go bad and/or the GEM on the drivers side has an issue.
Next spot to check is the shift motor on the Tcase. 2 plugs for it, one to run the motor and one to sense the position
All of the above is relevant to my 02.
does it work if you manually lock the hubs? if yes then its an issue with the hubs/vacuum setup. If not then it's another can of worms.
If the light on the dash is on its because the truck thinks the Tcase is in 4x4, if it isnt then theres a 4x4 control module above the glove box that can go bad and/or the GEM on the drivers side has an issue.
Next spot to check is the shift motor on the Tcase. 2 plugs for it, one to run the motor and one to sense the position
All of the above is relevant to my 02.
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Freshman User
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My HVAC doesn't default to defrost so I don't think it's a vacuum issue. My 4x4 does work with the manual hubs but not on the fly. The light comes on at the dash when I switch it on. My truck is an 01 Superduty. I will check some of the other things you suggested.
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Freshman User
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Fuses are all good and will check the solenoid again myself this afternoon. My buddy who is a heavy equipment mechanic helped me go through everything and he thinks it's the computer module on the drivers side by the fuse panel which he was pretty sure needed to come from a dealer as it needed to be programed. I was trying to do some more troubleshooting before I sent it to the dealer for my $1000 bill.
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Joined: May 2013
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Has to be a vacuum problem. You say that the lines are good but how did you check them?
A visual check wont do.
I recently delt with this and disabled my esop so my defrost would work.
A visual check wont do.
I recently delt with this and disabled my esop so my defrost would work.
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Postmaster
Joined: Apr 2012
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From: North Georgia
Also...
Check to see if the transfer case is shifting...
In park... in 2wd... reach under and try to spin the front drive shaft...
It should spin freely if the front hubs are unlocked.
Now turn the **** to 4x4 and check the drive shaft again...
Now it should NOT spin if the 4x4 light is on.
Since your 4x4 light runs off a sensor on the shifter motor... im assuming that your case IS shifting as it should... but your esof selonoid is dead...
If the transfer case IS shifting into and out of 4x4 high... then your computer/gem is fine.
Check to see if the transfer case is shifting...
In park... in 2wd... reach under and try to spin the front drive shaft...
It should spin freely if the front hubs are unlocked.
Now turn the **** to 4x4 and check the drive shaft again...
Now it should NOT spin if the 4x4 light is on.
Since your 4x4 light runs off a sensor on the shifter motor... im assuming that your case IS shifting as it should... but your esof selonoid is dead...
If the transfer case IS shifting into and out of 4x4 high... then your computer/gem is fine.
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So it ended up being a bad seal on my right front hub. I spent the weekend going through everything again and discovered the leak taking my time with each area. On a side note my GEM is going bad. My dash lights and parking lights are staying on after I turn my truck off and the only way to turn them off is disconnecting both batteries. I found out today that they are discontinued and the only way to find one is off a salvage truck. Does anyone have a source for a GEM?
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