View Full Version : Service 4WD System

May 20th, 2018, 09:11
I pulled the boat to/from the lake yesterday, and put the T-Case in 4-LOW to back the boat up a grassy area where I store it. When I got done, the T-Case would not come out of 4-LOW, and the Service 4WD System message was lit.

After a few re-starts, I got it into 4-HI and put it in the garage.

After a restart the T-Case is stuck in Neutral. Sometimes I can get it engaged enough to get it to move forward (Which doesn't help because it was driven into the garage).

If I turn the key on, but don't start, I hear the fuel pump, then a few seconds later the transfer case motor. Sometimes it grinds for a tiny bit, sometimes it carries on for some time.

Sounds like a bad selector motor to me.

Has anyone had experience with this? Can I get underneath and manually select 4-Hi just to get the thing going?

May 22nd, 2018, 11:12
I've been putzing with it and looking at the FSM. Don't have a code reader for the FDCM, but I am getting voltages at the shift motor connector.

The setup is interesting enough. The shift motor contains a motor, electric clutch, 3 sets of planetary gears, and what I can only surmise is a potentiometer. The Electric clutch must disengage for the motor to move, and the POT keeps track of the shaft position.
If the Clutch does not release, the motor can not turn.

Took the shift motor apart and found that a bit of case lube had made it's way into the motor and made it past the gaskets. I cleaned it all off, cleaned up the commutator and reinstalled it. Still no go and figured the sensor at the base of the unit had gone kaput.

I found a place in town with a new motor, so I replaced it $370 - no go :(
So now that I look at it, I think the issue is the Clutch is not disengaging, and is killing the motor.
That's probably why I've been reading about people who have had the recall done having to replace the shift motor afterwards.

Anywho, Along the way, I found I can manually select the transfer case by moving the shaft the motor engages with. As this is reachable without lifting the vehicle, it seems like a reasonable emergency ""Fix"". I'll need that to get it to the dealership...

This is starting to sound expensive - Volvo AWD Service expensive :(

Rob Mayercik
May 22nd, 2018, 11:34
if you can move the shaft by hand and select the case, perhaps a linkage could be improvised to replace the motor with a manual shifter?

May 23rd, 2018, 06:30
There is actually a write up on one of the forums where a guy was working on manual control of the motor which would bypass the FDCM completely.

I took it to the Dealership this morning.
They have a Scan Tool which will read the FDCM's codes and I'm really interested to see what they come up. According to Chysler's records, my vehicle has had both the recall solutions for the T-CASE shifting issues done.

May 25th, 2018, 09:25
Here's the Tech's diagnosis.

Reset Service 4WD code using Scan Tool.
Reinstalled Customer's new Transfer Case Selector Motor.
Tested Transfer Case in all ranges and Road Tested.

Looks like I did 1/2 the diagnosis, and they did the rest.
I am real confident the original motor was not working correctly, but having to have a special tool to talk to the FDCM was keeping me from completing the repair.

I guess I need another tool to work on Jeeps now :O

Rob Mayercik
May 25th, 2018, 10:32
Good to know. Might want to provide details on the scan tool for future reference if it's something special.