Truck: 2014 Ram 1500 Sport (5.7)

I just started getting a bunch of error messages and am suspecting it's a CAN buss (CAN bus?) issue? I can't find any info online on how to locate / replace the CAN buss on a 2014 Ram 1500. Any pointers on where it is or how to easily remove/replace it would be appreciated.

The backstory:

Getting these error messages on the dash display:
- Service Shifter
- Service Transmission Continue in D do not shift or turn engine off
- Service Electronic Braking System
- Service Trailer Braking System

Went to a local shop and had them read the codes...there were over 7 (more than a screenful). I should have grabbed what the specific codes were, but they were all "U" communication codes. I had the tech clear the codes assuming they would trip again if it wasn't just something random. Again got the "Service Shifter" error within a day (not all the other messages though). Bought a code reader and I only have a couple codes now:
- U0416 Invalid Data Received from Dynamics Control Module
- U0100 Lost Communication with ECM / PCM
- U0121 Lost Communication with ABS Control Module "A"

I've checked a bunch of fuses...can't find any issues there. (Clearing codes shouldn't eliminate error messages if it were a fuse, so I don't think it's a fuse blown).
Looking online for info about U codes leads me to stories of these kinds of issues being due to a CAN buss issue.

Questions:
- Would you suspect a CAN bus for these codes?
- Where is it located?
- Any other things I should check?

I don't want to go ripping out the dash, console or seats on a wild goose chase, so hoping for a guide on how to locate the suspect part.

Thanks in advance.

 

This is one of those problems were you are going to NEED a service manual to properly troubleshoot. Should be able to download one in PDF format from various places, most likely the publisher though, Bishko. Chiltons et. al. will NOT be sufficient, it has to be an actual factory service manual.

 

The CAN bus doesn't really have a single location, it's the data bus that connects pretty much all of the modules throughout the truck. There's probably a high speed CAN bus for some of the modules and a low speed CAN bus for less critical modules.

Since you mention a communication issue with multiple modules, this sounds pretty similar to an issue I recently fought with my 2018 Charger Daytona. I too had multiple modules with intermittent communication faults. Using the wiring diagram and my scan tool with the topology map for the CAN bus I was able to determine that all of the modules with communication issues were powered by the same relay in the fuse/relay box. When I checked power to the modules during a time when the communication faults were present, I discovered that the modules were only receiving 7-9 volts. I pulled the 70amp relay and confirmed that it had good battery voltage to the sourced side of the relay, but several volts were being dropped due to a bad internal connected of the switched side of the relay. I replaced the 70 amp relay and all my module communications issues were immediately resolved!

I spent a lot more time tracking this down than I typed up above, but this is the gist of the process. Hopefully the issue with your Ram will be as simple and inexpensive of a fix!

-Rod

 

In case you're interested in the long story, I posted about it here: https://dodgeforum.com/forum/dodge-charger/451275-don-t-do-what-i-did-made-a-simple-issue-tough-picture-heavy.html

-Rod

 

Thanks Rod. I'll take a look at your write-up on your issue.

I guess I'm really asking where the CAN bus "star connectors" are located. The connector where a bunch of modules all link up. I've seen a number of videos where techs find faults in them. I just can't find a video showing a tech working on my type of Ram where they show how they get to the CAN buss connector.

Lyle

 

Ahh, okay. Fortunately I have not had a reason to dig for the Star connectors on my 2014 Ram. On my Charger there was one located on the back side of the glove box that was pretty easy to get to, I'd kind of expect one to be in a similar location on the Ram. I also recall reading about installing SGW bypass cables on the 2018+ Rams and accessing the location for that from behind the radio cluster, so maybe there's a Star connector behind the center stack. I'd also not be surprised to find one under the rear seat area, but sadly these are all just guesses by me. I'll have to give some thought to whether I have a manual that might better describe the locations.

-Rod

 

It appears there are three, and all three are in the front of the cabin. The Instrument Panel location appears like it may be the easiest to access from the images.
-Rod

2014 Ram Star

2014 Ram Star

2014 Ram Star

 

Thanks Rod. This is super helpful. I appreciate the effort you went to for this!

Lyle