So I have a 2003 Dakota 4.7L with the NV133 transfer case that is stuck in 4WD. Currently there are no lights on the 4wd switch. I've replaced the TCCM to no avail, but I wonder if I just got a bad refurbed TCCM.

As far as I can tell, the TCCM is not sending the 5V ref voltage to either the 4WD selector switch or the transfer case position sensor. The switch tests ok (correct resistance based on position). The transfer case shift motor also tests ok (jumped 12V to the leads). The TCCM is correctly sending 10V to both motor leads as well, and the motor was replaced about 6 months ago anyway.

With black 4 pin and black 16 pin plugged into the TCCM, I get 5V at the TCCM grey connector pins B8 and A8 (Y/LB and Y/DB). However, as soon as I plug in the grey connector, the voltage drops to ~0.6V. I've checked the connections, and they're nice and tight. The voltage drops whether the 4WD selector switch is plugged in or not.

Any ideas?

 

Welcome to the forum.

What happens if you disconnect the connector at the mode sensor and then plug in the grey connector at the TCCM? Possibly there is a short in the wiring or the mode sensor has failed.

 

Good question. I'll have to check. That'd explain why I get the voltage drop in A8 going to the mode sensor...but shouldn't the 5V going to the selector switch at B8 still work? Also, is the mode sensor part of the transfer case motor assy. (meaning, it'd also be relatively new since that motor was replaced recently)? Reason I ask about the mode sensor is that motor and assy. should still be under warranty, and I can probably get the shop that did the work to replace it gratis.

The motor was replaced by a shop because the 4wd fuse kept blowing out. Prior to the no lights on the switch, there were a handful of instances where the transfer case would try to shift back into 2wd and fail (you could hear the motor cycling). Then one day, no lights, no more trying. To be clear, this is not my personally owned vehicle...it's owned by the project I'm currently working on, and I'm just trying to keep it running on a shoestring budget. Maintenance has likely been spotty at best.

Thanks!

 

If there was a short in the wiring to ground between the TCCM and shift motor/mode sensor it may be the cause of the 5v dropping out when you make the connection. Just trying to eliminate that.

The shift motor and mode sensor are an assembly.

Which fuse kept blowing? There are 3 in the system. One under the hood and the two in the junction block by the drivers door.

 

Ok, so unplugging the sensor eliminates the voltage drop, which tells me its an internal short/problem with the sensor. I did spray out the connector with WD-40 and give it a liberal gob of dielectric grease in case the short was due to water ingress at the connector, but no dice there. Hopefully the motor assy. is warrantied and I can just have the mechanic replace it again.

I had been thinking the 5V pins to the selector switch and the sensor were sourced separately inside the TCCM...but of course there'd be no real reason to do it that way.

The 20A fuse under the hood kept blowing. I forget what the explanation from the mechanic was...possibly oil contamination inside the motor itself (although it couldn't have come from the transfer case, so who knows).

 

Ok, truck is back from the shop. They warrantied the shift motor, but said they won't do it again. Apparently the motor was full of water, which begs the question: are the electronic shift motors on a 4wd system seriously not sealed against water ingress? Love to get my hands on the designer who thought that was a good idea.

 

Glad it's fixed. I've never heard of water in the shift motor, doesn't mean it never happens though.

Sounds more like a bad seal in the motor and it should be under warranty.

 

Yeah...I talked to them again, and apparently this is the second time they've replaced that motor with water in it. The replacement is an A-1 Cardone unit, which makes me think it's just a crappy replacement. I bet a Mopar unit would have been sealed properly.

Anyway, thanks for the help chasing down the problem!