For you guys with electrical experience, here is an issue I have been dealing with for several years. Since the van was new, we have had an issue of the instrument cluster will shutting off for a few seconds while driving. In addition to the instruments, the turn signals also stop. The lights and wipers seem to be unaffected. While under warranty, the instrument cluster and the body control module were replaced along with a cable harness for the BCM. The problem would go away for as much as a year and then pop back up! The last thing I did in the spring of 2022 was to remove and clean grounds. And again, no issues until yesterday when the cluster started shutting down. Although this time, it stayed off for several minutes.
I only have a fairly basic scanner so, no codes are being detected by it. I suspect a "loose" wire but quite frankly, I'm at my wits end trying determine where that may be. Any suggestions are greatly appreciated.
Gary

 

Can you post your vehicle info please?
Intermittent electrical problems can be a nightmare. You just have to work inch by inch, wiggling each wire, unplugging and inspecting each connector... The diagnostic scanner probably won't help, but a multimeter with continuity testing, test light, or circuit tracer will.

 

Opps! 2014 Express 4500…

 

Update: I’ve replaced grounds and measured voltage and have not resolved this issue. I have measured both the battery voltage and ignition voltage at the Instrument Cluster connector. Both stay on even when the gauges go to zero.
I have learned a bit more about the symptom. When the gauges drop off, the Low Fuel light comes on along with the low fuel level message on the information screen. In interesting that doesn’t happen every time. If the light doesn’t come on, the display shows dashes.
I’m beginning to think it may be a canbus issue with the BCM and/or BCM. I don’t have the proper scanner to look for com faults. Can someone recommend a scanner capable of recording module communication? I looked into the Tech2 clones but, not certain they will work in a 2014 chassis.

 

If it were a bus issue, I would expect that you get check a engine light and 'U' communications fault codes.
To read these you would need an "all system" diagnostic scanner. (https://carkiller.com/scottykilmer/h...-should-i-get/)

For OEM equipment you would need an MDI2 interface , and a GDS2 software subscription. An expensive proposition. Really only appropriate for pro shops. https://www.acdelcotds.com/subscriptions
Tech2 is not compatible with your van. https://www.gmparts.com/content/dam/...tool-sheet.pdf


I would grab some schematics from gmupfitter.com and start measuring resistance/continuity on the applicable circuits. You also have to consider the possibility the cluster is faulty. Since you only get the issue while driving, try bumping it around.

 

Thanks for the feedback. I’ve spent much of the morning reading about scanners! I think I need one that shows live data streams so I can monitor such when the gauges fall off…still researching and learning!
I do have the upfitters documents. I have been using it to locate grounds, 12v supplies etc. still poking around.
This issue has existed since new and has gone from happening a few times a year to happening several times a minute. GM actually replaced the cluster once along with the BCM. Or, at least that’s what the service docs say. Since removing the cluster, I’m not so convinced they changed it. I may look for a used one to swap in. I do have a used BCM that will need programming. Unfortunately for me, the local GM dealer will not program it since it is used.
Thanks again!

 

I expect your data streams will look fine. Otherwise you would get diagnostic faults, or the engine may not run at all. I think your problem is affecting your cluster only.


you would need to find an auto electrical specialist or tuning shop

 

I think I found a shop in the area that will copy my bcm and upload it to the used unit. Going to take it there on Wed.
Maybe I’ll through a used cluster in it just to see what happens.

 

Well, a new BCM seems to have resolved my issues!

 

thanks for reporting back