AWD acts like vehicle is in 4x4. NEED HELP.

[jkloster]

Problem with my 2004 5.4 L Eddie Bauer Expedition. I purchased new and have 94,000 miles on it. When I put it in AWD it engages 4x4. My vehicle will no longer run in AWD. When I select the AWD mode it puts the vehicle into 4x4. I get the difficult turning and tire scrub. The 4x4 L and 4x4 H settings both work fine but the AWD no longer works correctly.

I first thought transfer case motor may have been bad. When I removed it I saw that it only puts vehicle into 4x4 H and 4x4 L. It doesn't have anything to do with putting vehicle into AWD. The transfer case motor was working fine. Which made sense because I have no problem putting the vehicle in 4x4 H or L. I installed a new one just to make sure.

I then checked the 4WD Hub Locking Solenoid and vacuum system. It was working fine - engaging the front acctuators correctly. Which also made sense because the 4x4 settings are working correctly when vehicle is set for 4x4 H or L. I replaced the solenoid just to make sure.

Does anyone know how the AWD system is supposed to be activated when the dash selector is set to AWD and why it is now putting my vehicle in 4x4. After selecting the AWD mode I removed the transfer case motor to make sure my AWD setting wasn't causing the transfer case motor to mechanically set my transfer case to 4x4. This wasn't happening. When I move my selector to AWD the transfer case stays at the 2x2 setting like it is supposed to.

Could the problem be caused by a bad transfer case control module?

My computer is not generating any DTCs.

Thanks for any information you may have on this.

 

[whtbronco]

I believe the transfer case shift motor controls both A4WD and 4H combined, 4L is separate. So it sounds like the motor is working fine. To me it sounds like the lock up solenoid is not working, which I believe is called a coil and is inside the back half of the transfer case(output shaft housing) images below. A4WD has a limited slip diff or maybe it's an open diff in the transfer case, 4H and 4L lock the transfer case.

The hubs are engaged(4WD mode) by default. When we start the vehicle and produce vacuum they disengage if we've selected 2WD.

You mentioned not seeing any codes. Does that mean you have an ODBII scanner that can run Actuator tests? If so what does it show when you command the transfer case to A4WD. If not I'd look at the switch and wiring as a starting point.

Here's the transfer case connector and it shows only 3 motor positions: 2WD, A4WD/4H and 4L.

 

[jkloster]

Thank you very much for the reply.

Thanks for transfer case pin setting / circuit diagram. I don't understand it completely, but if the 2nd setting is A4WD/4H, it makes we wonder why my transfer case motor doesn't turn my transfer case to the 2nd setting when I turn my dash knob to AWD. The Transfer case stays at the 1st setting (2WD) when I move my knob to the AWD setting, yet my vehicle goes into 4x4 mode.

When the control knob gets set to AWD, the transfer case shift motor does not switch the transfer case to the 4X4 H setting. It stays on the 2X2 setting in the transfer case's number 1 position. The 3 settings labeled in my transfer case (visible after removing the transfer case motor) are 2x2, 4x4H, and 4x4L. There is no AWD label in the transfer case (although you are saying the diagram is showing that the A4WD & 4H settings are the same number 2 position). I thought it was odd that the setting in the transfer case stayed on the 2x2 setting (#1 position) when I put the vehicle in AWD. I could hear that the transfer case motor didn't move anything when I switched the control knob to AWD and I also confirmed that it didn't move by removing the transfer case motor and visually saw that the transfer case was still set to the 2x2 setting (#1 position) after I had moved my knob to the AWD setting. It made me wonder how the vehicle could go into 4x4 mode the way it does when I set the control knob to the AWD setting when nothing moves in the transfer case. I'm guessing you understood that in my first post. I didn't completely follow what you were saying.

Based on what you said (that the hubs are engaged in 4x4 mode by default, and disengage by vacuum at startup if the vehicle is set in 2x2 mode): I'm guessing that this has something to do with the fact that the transfer case motor doesn't have to move the transfer case setting to the #2 position (4x4 setting) for my vehicle to go into the 4x4 mode the way it does when I move my control knob to the AWD setting. It does make me wonder how the vehicle can start operating in the 4x4 mode without the transfer case being set to the #2 position (4x4 mode).

I did not run any actuator tests with my scanner. I'm not sure if it can but I will get one that can if mine can't. I just ran a general scan to see if there were any fault codes and I didn't get any fault does. Thanks for suggestion.

Thanks also for images of output shaft housing and recommendation to check the lock-up solenoid/coil. I didn't know about that.

I will also check the switch and wiring. I will reply back after I check these things.

Thanks again for your time and advice.