Service 4wd issues

Big Block 88

Big Block 88

Multiple choice muscle
Nov 3, 2008
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Howdy all. I have been going rounds with 07 classic and its 4wd system. It is the pushbutton and the dash is saying service 4wd.

I changed the switch in the dash and still no help. I chaged the actuator in the front diff and still no help. I also checked the fuse and it was good but switched in a new one any way.

When u go from 2 hi to 4 hi the trasfer is shifting the front and rear driveshafts are locked in when switching from 4 hi to 2 it is disengaging the front drive shaft just fine. So im assuming the issue is in the front end somwhere.

Any ideas where i should start to look? I use 4wd pretty regularly around the house and ranch but it has been out for about 4 months now. With winter coming i need it back asap.

Thanks for any and all help
 
clrussell

clrussell

pro-procrastinator
Sep 23, 2013
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So the transfer case unlocks when you go to 2hi from 4hi? But the driveshaft doesn't?

Is there actually a message on the dash saying service 4wd? If so you should be able to read transfer case codes with a good scanner.


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C

Cougar281

Well-known member
Sep 11, 2006
1,823
261
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St Louis, MO
Big Block 88 said:
Howdy all. I have been going rounds with 07 classic and its 4wd system. It is the pushbutton and the dash is saying service 4wd.

I changed the switch in the dash and still no help. I chaged the actuator in the front diff and still no help. I also checked the fuse and it was good but switched in a new one any way.

When u go from 2 hi to 4 hi the trasfer is shifting the front and rear driveshafts are locked in when switching from 4 hi to 2 it is disengaging the front drive shaft just fine. So im assuming the issue is in the front end somwhere.

Any ideas where i should start to look? I use 4wd pretty regularly around the house and ranch but it has been out for about 4 months now. With winter coming i need it back asap.

Thanks for any and all help
Click to expand...
You're going to need to get the DTCs from the TCCM to figure out what it's unhappy about.

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Big Block 88

Big Block 88

Multiple choice muscle
Nov 3, 2008
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I am showing no codes at all. Efi isnt reading any codes but the dash does say service 4wd.

The transfer case is doing its job as the front drive shaft is locked in 4wd and unlocked in 2 hi. By that i mean when i put it in 4 hi and get under the truck if i spin or just slightly rotate the front shaft the rear shaft is spinning also. When i go to 2 hi the front shaft spins freely and is not moving the rear shaft.

How do you relearn the encoder motor? I can hear the transfer case clickin in but i dont hear anything in the front axle when it should be engaging the front axle.
 
Awenta

Awenta

Active member
Sep 28, 2014
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If the message is on then something is there. Don't know if the v2 has access to it though.

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Duramax One

Duramax One

Vote for Pedro
Aug 11, 2012
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My V2 has read all the 4x4 codes I've run across, so there may be a U1000 (Class 2 data bus issue) code indicating a communication problem between modules and the front axle, transfer case, etc. Check to see if you have any U1000-series codes as well as check for U1300, U1301, or U1302 codes (indicating a data bus short or open).

As a sanity check, you should jack up the front end, place the vehicle in 4x4 (high or low - doesn't matter) and see if the front wheels are connected to the front drive shaft.

Since the DIC is indicating a 4x4 issue, I am very surprised that you aren't getting any codes, unless there is one of the U-codes indicating a general loss of communication.
 
Awenta

Awenta

Active member
Sep 28, 2014
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The v2 would definitely pickup a U code though

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Big Block 88

Big Block 88

Multiple choice muscle
Nov 3, 2008
4,665
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Kansas when I am home
I do have a UO106 and a UO101. That just showed up after i did a trans relearn. Im getting curious now about the issues i am have with my cts after doing the dsp5 reflash. i pulled the ground wires to body mount under the drivers door and cleaned them up. But that didnt help either

I had it on wet grass this morning and with minimal throttle it was spinning the rears i hit 4 high and nothing happened the light on the dash switch just flashed by the 4 hi i could hear the transfer case shift but nothing locked in on the front
 
C

Cougar281

Well-known member
Sep 11, 2006
1,823
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St Louis, MO
One thing of note since you have an 07 classic..... Prior to converting my 04 to a full LBZ, my V2 could, at the very least , clear codes in my hvac module. It *might* have been able view them as well, I don't recall. But after I converted to LBZ, my V2 only communicates on the GMLAN bus. No class2. So it no longer sees or clears my hvac codes. Need to get out my tech2 to do that.

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Big Block 88

Big Block 88

Multiple choice muscle
Nov 3, 2008
4,665
0
36
38
Kansas when I am home
Well speaking of the hvac does the fuse under the hood for it still affect the 4wd? I had an older 6.0 gas truck that had the 4wd go out and if i remember correctly it was the hvac fuse that caused it. But this trucks hvac is working fine though it does decide for you if u get inside air or out side air

Tomorrow before work i am going to pull the front axle acuator and see if it moves while my pops hits the selector buttons in the cab. This is why i miss the fords old lock out hubs. I may have broken a few hubs over the years but i always had my front drive when i needed it.

Thanks for the help fellas if you can think of anything at all it could be please let me know i will try just about anything at this point. Someone mentioned earlier here that i could reset the encoder mototr?
 
Big Block 88

Big Block 88

Multiple choice muscle
Nov 3, 2008
4,665
0
36
38
Kansas when I am home
Changed the output shaft sensor on the transfer case not sure why. Somebody told me that was what triggered the front axle engagment. I saw a brown wire like the front diff actuator so i figured screw i will change it out.

So any way i still dont have 4 wd. I do have low range but it is the rear axle only. Im at a loss fellas
 
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