2003 Dodge Durango, 4.7L

I am in desperate need of assistance troubleshooting and repairing my 4WD. Obviously, it's the middle of winter and it's important here where I live, and without it I'm pretty much dead in the water. The 4WD worked fine up until a couple days ago. It's always worked great until it didn't, ha. Below are some bullet points of things I HAVE tried, HAVE tested, and HAVE replaced.

Basically, what's going on, is I AM getting power and ground to the 4WD switch. When I flip the switch from 2Hi to 4Hi, ALL of the lights on it light up and then begin flashing until "Service 4WD" appears on the cluster. If I switch back to 2Hi, 2Hi lights up and after driving a few miles "Service 4WD" will disappear. Obviously the 4WD is not engaging. I am NOT hearing the TCM engaging/trying to engage when I flip the switch to 4Hi.

• I have checked the 20A fuse under the hood.
• I suspected the TCM/encoder had failed, so I replaced it with a brand new one.
• I inspected the wire harness and plugs for the TCM/encoder, it appears good with no broken wires, etc.
• I tested the TCCM blue box according to instructions I found online, I am getting +12V and +5V at all of the correct locations.
• I tested the 4WD dash switch and it appears to also be getting +12V and +5V in all of the correct locations.
• When replacing the TCM/encoder, I put a wrench on the transfer case key and turned it. It moved, so that tells me the transfer case isn't bound up.
• Everything else works. power locks, windows, headlights, interior lights, so I'm leaning against a failed BCM.

On the transfer case selector dash switch,
Pin 1 to Ground is +5 VDC, key on.
Pin 5 to Ground is +1.71 VDC when I turn the switch to 4Hi.
Pin 7 to Ground is +12 VDC, key on.

On the TCCM blue box thing,
On the black 4 pin connector, Wire A to Wire B is + 12 VDC, key on.
The PCI Bus wire A1 violet/yellow to ground is +0.70 VDC to +1.10 VDC, key on.
Both wires, A8 and B8 have +5 VDC to Ground.
I DID notice though that on the black 4 pin connector, I am reading +12 VDC on BOTH the C & D wire, which go to the TCM/encoder. I thought that was a little odd, as I assumed the TCM/encoder worked by sending +12V to opposing poles of the motor to turn it.

Based on what I'd found online to troubleshoot and test the TCCM box, it appears to check good.

I am at a loss here, and need help from someone who is VERY experienced and knowledgeable about the 4WD system. I am prepared to do the nuclear option and bypass the TCCM box with a momentary switch and wires direct to the transfer case motor, but don't want to lose my shift on the fly functionality. It's nice to flip it in 4WD when moving if I need it.

I DO have the TCCM box and the dash switch "hanging loose" under the dash, so I can probe wires there and report back with readings pretty easy. Underneath the vehicle though, I'd prefer to not roll around down there to probe transfer case wires if I can keep from it. If it's needed, I'll make it happen though.

Someone, please, I beg of you..

 

You have posted this same thing in two different areas. (2nd gen Dakota and 1st gen Durango) and failed to mention the vehicle you are referring to.

Please add your vehicle information to the post so the correct technical section can be assigned.

 

My apologies. I went back and edited the posts.

 

Adding further troubleshooting information here:

I have checked continuity on several TCCM wires.

A1 - violet/yellow - PCI Bus continuity to data link confirmed, floating voltage confirmed
A4 - dark green/brown - 4WD Lo indicator continuity to mode switch confirmed
A5 - dark green/orange - 4WD Hi indicator continuity to mode switch confirmed
A6 - yellow/dark green - mode select continuity to mode switch confirmed
A7 - solid yellow - mode sensor ground continuity to mode sensor confirmed
A8 - black - ground continuity to chassis ground confirmed
B4 - yellow/light green - neutral lamp indicator continuity to mode switch confirmed
B5 - pink/gray - 2WD Hi lamp continuity to mode switch confirmed
B8 - ground - black continuity to chassis ground confirmed
B8 - yellow/light blue +5V to mode switch continuity to mode switch verified, 5V to mode switch verified
A - black - ground continuity to chassis ground confirmed
B - light blue/red to 20A fuse in PDC continuity verified, 12V verified
C - dark green/violet to TC shift motor continuity verified, +12V key on verified
D - dark green/white to TC shift motor continuity verified, +12V key on verified


Some additional "This is what I DO know" notes..

- The transfer case motor & mode sensor are brand new, replaced with a quality part from O'Reilly's
- The TCCM appears to check good based on voltage readings present.
- The TCCM appears to be grounded properly, otherwise I wouldn't be reading voltage correctly.
- Fuse 20 in the PDC is good.
- Fuse 11 is good.
- Fuse 12 is good.
- Transfer case motor plug is getting +12V to BOTH wires (I have read this is correct?)
- All wires from the TCCM to the 4WD mode switch are showing continuity & proper voltage

 

The more I look at this, the more I am leaning towards a wiring issue from the TCCM to the transfer case motor/mode switch.

The TCCM appears good.
The 4WD switch appears good.
The wires between the TCCM and 4WD switch are good.
The transfer case motor/mode switch is brand new.

I need to get under the truck and probe the transfer case motor/mode switch wires for their respective grounds and +5V. When I replaced it, I quickly examined the connectors and harness, but did not peel back any of the loom tubing to closer examine wires. I'm really thinking there's an issue in that harness somewhere..

 

It's still possible the control module is toast as well.....

 

It's funny you mention that.

So I went out this morning to test and probe some more wires. I wanted to check for +5V on the dark blue/yellow going to the TC motor encoder/sensor. Nothing. This confused me, because when I checked it a few days ago, it was present! So I went back and checked the +12V on the blue/red feeding the TCCM. I read a whopping 4 volts there instead of the 12 it's supposed to be.

Check the fuse in the PDC under hood, it's good and sending 12V to the TCCM.

When I check for 12V on the backside of the plug, I'm getting 4 volts. When I unplug the plug and check it, I'm getting 12. Obviously something isn't kosher there.. Is it possible that the TCCM blue box was failing, and now has finally punched out for good? The TCCM checked good a few days ago and the 4WD switch mode lights were lit up. Now, the 4WD mode switch is DEAD and I have the Service 4WD light on the dash on.

Very strange..

 

I hate the electronic t-case shifter..... Electronic parts that are prone to failure, and generally when you need them the most... I simply do not know enough about those systems to properly troubleshoot them though.... A service manual would be real handy to have at this point.

 

Lol, Then Ya' need a library to keep 'em in these days............

My '02 Durango set less the basic FSM.