I have a 2011 Ram 1500 with the SERV 4WD light on at all times. Originally it would come on intermittently, but would reset and go off when you turned the truck off, however now it stays on at all times no matter what. It has been on for months now and I cant use 4WD. There are no DTC's stored in the computer. My cruise control still works so that leads me to believe that its not a wheel speed sensor. None of the TSB's line up with my issue because there are no associated DTC's, so that makes me feel that it's not needing a re-flash. The light never came on as a result of me trying to engage 4WD, so that makes me feel like it's not the transfer case shift motor. Temperature outside makes no different since it is on at all times.

Any ideas from anyone? I won't take this thing to a dealer unless I have exhausted all other options. Thanks for the help!

 

I'm not sure what scan tool you are using, but if it's a standard over the counter consumer-grade scan tool, it is probably only able to read out Powertrain ('P') codes and not able to access the 4WD system to read and display associated diagnostic codes. With that in mind, it may be premature to say it doesn't align with any of the TSBs.

If you have an ELM327-based OBD-II dongle, downloading AlfaOBD may be the most cost-effective way to pull DTCs from the 4WD system.

-Rod

 

I'm using a garbage OTC scanner that doesn't have access to everything. I work mobile fleet maintenance and my partner has a Snap-On Solus scanner, so I'll borrow that thing from him and give it a try. Unfortunately we don't have access to the manufacturer specific scanners that can read everything on that make.

 

Blue Driver is the best diagnostic tool I’ve found for any vehicle. I’ve had transfer case motor problems with my 2007 4X4 diesel. Ive changed out 2 Transfer case drive motors from Rock Auto parts house. Each motor electrically functioned the transfer case into 4 wheel high and low after I changed them out but after a while when functioning the modes they stuck in the RV tow neutral position stranding me. Fortunately I had my son tow me home 🏡. The Blue Driver blue tooth analyzer tells me that the 4wheel control circuit is open again. Trying to find the correct transfer case motor that matches my Transfer case. The 4x4 electric control woes!!! Tom

 

What exact code are you getting? It may not be the motor at all.

 

Code is: C140D Transfer Case motor control circuit open.
Tom

 

that sounds more like a wiring problem. changing the motor just moves the wires enough to make em work again for a bit.

 

I’ve pulled out the Transmission cable harness and continuity verified every connector in that harness verifying the pin connections as well. I’m convinced that Rock Autos Mexican or Chinese Crank case Motors internal computer indicating mechanical or SS switches are defective and opening when exercised.Trying to find the best one for the money. I’ll never trust the electrically controlled 4Wdr again. Once I get it working I’ll leave in 2 wheel! I just completed a 1,111mile trip to a family situation. To and fro!!! Damned glad I didn’t test the 4Wdr repairs on I-10!!!! Tom

 

By the way, that Mexican wiring harness is of the poorest Quality I’ve ever seen. Mexico harness people are not quality control checked if the continuity machines indicate a pass!! My bet!! Tom