Hello again, so our ‘14 4500 cutaway chassis has had an intermittent instrument cluster for the past five years. Chevy found a chafed wire in the BCM wiring at the module connectors. They repaired that, replaced the cluster and the thing work solidly for about 13 months. Since then, I have cleaned the chassis ground along with the one under the hood and just put up with the failure.
On a recent trip, the turn signals and the wipers joined in! Now when the instruments shut down, the wipers and the turn signals stop as well. This lasts only about five to fifteen seconds and then all is well for a half hour or so. This all starts after driving around 4-5 hours and continues the rest of the day.
I could use some expertise on just what may be common to all three of these circuits…any thoughts on where to start?

 

Looked for chafed wires again.

 

Okay, so I removed the dash and instrument cluster. Unplugged and re-plugged every connection I could get to, inspected all the wiring I could get to and put it back together. The good news is everything worked after reassembly. The bad news is I really didn't find anything "bad". However, I did find this jammed into the connector on the steering column. I appears to be a locking device but it didn't appears to accully belong in that specific connector.
We won't be taking any long trips for a few weeks, so there is no way to determine it anything was truly fixed. I'm beginning to suspect the BCM but, the dealer explains that they can't confirm unless they can duplicate the symptoms.

 

that looks a lot like a lock from a grounding splice pack. A janky splice pack would explain a lot of your issues.
gmupfitter.com has harness routing drawings to help you find where that came from.

 

Any thoughts on where it might belong?

 

they are all over the place. I think each B pillar has one, each door wiring harness, and several more inside the dash. Like I said, gmupfitter.com has the drawings you're looking for. Get studying.

 

I’m on it…

 

Making progress…I’ve at least identified each ground and its location. Next is tearing into some interior panels and such.

 

Sometimes something simple will help.
In this instance where the wipers and instrument cluster might share the same ground, if we 'provide a good ground to the wipers it will share that ground with the instrument cluster. It sure would save a lot of time and effort and accomplish the same thing.

 

The point of grounding distribution is to provide a good low impedance path for the current to go.
By doing what you say, the ground wire for the wipers is now doing double duty. Carrying more current than it was designed for. This can lead to even more electrical gremlins.
When it comes to wiring, fix it properly. Don't add to the mess.