2005 Expedition 4x4 Issue - Lights Not Working, 4LO Won't Engage

[mr7743]

Hey fellow ford owners,
I've got a puzzling 4x4 issue on my 2005 Expedition that I just picked up. Here's what's happening:

- 4x4 lights work during startup check
- When I engage 4x4, no lights turn on
- Auto 4x4 seems to work (message center confirms, tested in sand)
- 4HI light doesn't turn on when 4hi is turned on
- 4LO won't engage (keeps prompting to shift to neutral)
- IWE seems OK (vacuum to wheel hubs turns off in 4HI, 22+ inHg steady in 2HI)

What I've checked/know:

Lights are definitely not burned out (work on startup)
IWE pressure switch might be involved with lights according to one post I found on here? I've yet to confirm this

Any ideas what could be causing this? Any ideas on possible next diagnostic steps?
Thanks in advance for any help!

 

[whtbronco]

You will need to be in Neutral to engage 4LO. The overly complicated 4WD system in these trucks requires input from the transmission, wheel speed sensors, PCM and ABS.

This could very well be the shift motor. The shift motor only changes from 2WD to 4HI and 4LO. A4WD is engaged simply by energizing the coil that engages the clutch pack inside the transfer case. You can remove the shift motor from the transfer case by removing 4 10mm bolts, torque spec for the bolts is 89in lb. You can then shift the transfer case carefully manually with a pair of pliers on the shift shaft, turn the shaft slow and steady, don't force it.

You can also try shifting without the engine running. You should be able to hear the shift motor and the forks inside move if it's working. Selecting A4WD the only noise you should hear is the vacuum hubs engaging.

You can find lots of pics of the BW4416 transfer case in this thread:

Not so Good Vibrations

Based on the chart below I bet my scanner is reading the EPC solenoid pressure and not actual line pressure. I just can't believe that if my trans pump was around 20% of the low side pressure that it could even grab a gear. The EPC pressures I saw are on the low side of this chart, but within...

www.expeditionforum.com

With an OBDII scanner you can see what range is selected.

 

[mr7743]

Excellent information whtbronco, thank you!

Yes, when I'm in neutral and pressing on the brake and shift into 4LO, nothing happens (no lights come on), then I go to shift to drive, and once in drive it gives me the warning on the dash about shifting into neutral to engage 4LO (even though I just did that).

I will check out the shift motor tomorrow, thanks for that advice!

 

[mr7743]

An update:

I was able to get the shift motor off today, and indeed, it is not turning at all when the switch is turned. The transfer case shaft turned easily, and I was able to drive in 4LO with the shift motor off (just to make sure it was working. I also got 12 volts (car not running, just in the on position) to the 30A shift motor fuse under the dash. I didn't have anyone with me to check for power to the motor's plug.

 

[whtbronco]

Glad to hear the transfer case seems okay. The shift motors do fail, I just had to replace mine. Mine was also causing issues for other systems in the truck.

You can test for power at the connector without a helper just takes longer. You'll have to select the transfer case range you want, climb under and check for power at the appropriate pin.

Here's the shift motor connector pin out. Pin 8 connects to the coil wire that goes into the transfer case and gets power only in A4WD.

 

[mr7743]

thank you for the information!

I’ve never been great at electrical diagnostic, do I sent one end of the multimeter to chassis ground and one in the pin to test voltage?

And why are there 4 positions? (And only three locations for it to turn - ABCD vs 2Hi, 4Hi, 4Lo)?

 

[BlackCoffee]

I am not sure about 2005, but in my 2003 I had the exact same problem. It turned out to be the controls for air conditioning and heater. The circuit board went bad and messed up the buss. Found out that since 4x4 was an option and so was the upgraded front/rear heating and cooling, they were on the same bus. Pull the dash and disconnect the connector to the A/C controls and see if you get 4WD drive back.

 

[mr7743]

Oh that’s good to know, BlackCoffee. I’ll give that a try tomorrow!

 

[whtbronco]

Yep connect the positive lead from your multimeter to the desired pin and the negative lead to the frame.

There's 4 switch positions.
2WD is controlled by the shift motor
A4WD is controlled by the clutch coil in the transfer case, the shift motor stays in 2WD
4HI is controlled by the shift motor
4LO is controlled by the shift motor

 

[whtbronco]

BlackCoffee's idea is good too. Like I noted my shift motor caused issues for other systems and the issues and codes varied. I did get codes for the HVAC(EATC module) caused by the shift motor.

A scanner will help this quite a bit.

 

[mr7743]

I do have an OBDII scanner, but I’m reading no codes

 

[mr7743]

Unplugging the AC controls had no effect. When I had the motor out I tried to use a screw driver to turn the shaft on the shift motor, it was locked up solid. Should I be able to move that manually?

 

[whtbronco]

I doubt all scanners can read the 4WD module, and only high end scanners can control the 4WD module. FORScan can likely read the 4WD module with right adapter.

I'm not sure if you'd be able to turn the shift motor with a screw driver. I never tried. I wish I had kept 1 of the old ones I had so I could take it apart.

I am a big fan of testing to the point of positively identifying a failure before spending money, but in this case it does seem like it's the shift motor.

 

[mr7743]

Thatnks for the heads up. I hate to be a “parts replacer”, but sometimes I go too far in the other direction. New shift motor is on order!

 

[BlackCoffee]

I also do not know if you can turn the motor with a screw driver. It is a step motor that runs the transfer case to the correct gearing. You can remove the motor from the transfer case and see if it turns with the switch. At least that will isolate to a motor problem or an indication problem.

 

[mr7743]

Yes, I did try running it with the switch with no response. Also none of the positional pins on the plug had power, but the other pins did - which does seem to align with a post I found about rebuilding the shift motors online that said one of the main failures was a small bushing that would allow the motor to "lose its place". I assume if the motor had lost its place then the computer wouldn't know which position to apply power to.

 

[mr7743]

Just to follow up, I replaced the motor and everything functions perfectly. Lights on the dash are also functional again. You cannot turn the motors by hand even if they are working for any future diagnosticians

 

[whtbronco]

That's good news. It sure is nice to get things resolved.