Suburban Electrical Mystery

Bill Owner/Technician Michigan Posted   Latest  
Resolved
Electrical
Network Communications
2016 Chevrolet Suburban LS 5.3L (C L83 Flex) 6-spd (6L80) — 1GNSKHKC4GR345800
U151A
U1526
U1538
U1549
U1550
U1558
B1517
B1325
B3101

Hello group this Suburban was recently purchased my my customer from a local car lot I work with regularly… Customer states intermittently after starting the vehicle the lights (interior + exterior) will flash, blower motor will turn on/off, vehicle may stall but restart. And to top it all off they claim it has started its self a few times now too… seen it running in the driveway with nobody pushing the remote start?

I had the vehicle at the shop for 3 days last week and could never duplicate a issue or get any faults to reset. Customer took it back and 3 days later the weird electrical issues are back… The low voltage and communication faults listed were all present both times the vehicle arrived to me.

Vehicle battery is new/good. I have accessed the BCM and verified all connections, voltage and ground supply checked with a 3 amp bulb. There are NO software updates available for BCM on SPS. I have verified all fuses feeding the BCM to be proper and tight, I can not make any issue's happen shaking the harness at BCM or fuse panels.. I have scoped the LIN Bus 1, 2,and 3 at the BCM (X6 connector pins 9,10,16) pin 10 or LIN 3 seems to have a bit different of a pattern but i am not sure if this is a issue or not? I have yet to duplicate the vehicle issues myself :( I am wondering if the LIN Bus faults are just a result of the intermittent low voltage concern? What to test or inspect? When this problem does reoccur i dont feel i will have a lot of time to catch it in the act so where would you guys have your leads hooked up? 

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Adam Owner/Technician
Maine
Adam
 

Disable/remove remote start? Have seen similar issues in the past.

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Bob Diagnostician
Maryland
Bob
   

Yup​.​damn thing might catch fire. Tell them to park it outside,

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Bill Owner/Technician
Michigan
Bill
 

Adam how would that help the LIN Bus and low voltage faults as well as the flashing lights and blower motor cutting in and out???

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Jared Diagnostician
Maryland
Jared
 

Dont want to be too simple on this, but they dont have an aftermarket “pay to play box” in this, do they (like a Spireon Goldstar)? Ive seen people wire these things in completely wrong and cause some weird crap.

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Edward Owner
Texas
Edward
 

Jared You have a point,…

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Bill Owner/Technician
Michigan
Bill
 

Jared good idea but No aftermarket accessories have been found on the vehicle at this point we have looked…

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James Technician
Virginia
James
 

Is the remote start on this vehicle factory, or aftermarket? I hate intermittent problems like this! Very difficult to nail down unless you're lucky enough to have it in your bay while it's acting up.

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Bill Owner/Technician
Michigan
Bill
 

James - its a Factory Remote Start - i dont play around with aftermarket remote starts i remove them :)

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Mark Engineer
Colorado
Mark
 

Bill several years ago had some interesting electrical issues on vehicle. The owner had a windshield installed (poor workmanship). Water ran into BCM. isn’t BCM on driver’s side under dash where water could run into it and cause problems?

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Bill Owner/Technician
Michigan
Bill
 

Bill - yes BCM located under steering wheel area but no sign of water intrusion or corrosion at BCM or connectors

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Christopher Technician
Virginia
Christopher
 

Hello Bill. Sounds like fun. Look for add ons. Some of the stuff is really weird and no one seems to totally understand the functionality. I pulled a gps tracker (supposedly) off a Hyundai last year. It had 40 plus wires on it. Ignition, PCM, ABS some others, all tapped. That one had an intermittent no crank and stalled some time. Many U codes when it acted up. It was buried behind the center…

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Gerald Owner/Technician
Missouri
Gerald
 

Didnt thebolder models of these have problems similar to this and turned out to be the ground cable from the battery

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Sadel Owner/Technician
Ohio
Sadel
 

Bill, it sounds like you have covered the main steps, and it seems odd of how intermittent it seems to act up. I was just browsing on the wire diagrams based on what you say the customer is complaining about dropping out. so I looked at bcm for light flickering issue, looked at blower control for cut out issue, and looked at pcm or pcm/fuel pump related stuff for stall issue. There seemed to…

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Bill Owner/Technician
Michigan
Bill
 

Thanks for your time and ideas Sadel :) i will defiantly double check these grounds at the ground point

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Sadel Owner/Technician
Ohio
Sadel
 

I attached a pic of the bulletin i found just in case

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William Technician
West Virginia
William
   

I would chase down the remote start issue using logic as they are likely all connected: Remote Vehicle Start Circuit Description/Active The BCM receives a signal from the keyless entry transmitter indicating a remote vehicle start request. The BCM uses the following inputs to verify the system is ready for a remote vehicle start event: - Vehicle is not in valet mode - Low fuel level…

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Thanks
Bill Owner/Technician
Michigan
Bill
 

William always glad to hear from you when i am working on a GM! I forgot to mention i did contact onstar to verify subscription status as with a newly purchased vehicle i was concerned the previous owner may still have a mobile app to command starting and unlocking.. On star verified the subscription is in active and claims no possible mobile functions at this time. Thank you for PIT document i…

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William Technician
West Virginia
William
 

Glad to help. All the passed and failed codes are BCM related, but this B3101 interests me the most. If not a wiring issue, it is possible it is the RCDLR but all the LIN codes lead to the BCM. So does the troubleshooting. Good luck! and I HTHs.

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Michael Technician
Indiana
Michael
 

Is the LIn bus failure repetitive? If it is I would start disconnecting my LIN components until it straightened up.

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Tom Owner/Technician
California
Tom
   

The problem sounds like you have a short circuit in the LIN compponents, you stated irregularities with LIN signals. The issue will dissapear when you have a normal signal. All B Codes are for BCM Undervoltage or Overvoltage for more than the minimum allowed ( 2 volt difference ). B3101- Door lock is the code watch first, that is the car starting itself cause. Check the power mode. (Ignition…

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William Technician
West Virginia
William
   

With the Master/Slave LIN topology I would have to disagree with both above, you have 6 LOC (loss of comm) LIN codes stored in the BCM as passed and failed. There just so happens to be 6 separate LIN networks off of the BCM. A short or network failure on one LIN would not have an effect on the other separate networks, so that means you have 6 separate shorts. I doubt that to be the case. I look…

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Scott Owner
California
Scott
 

Hi Bill, With all of those symptoms I'd be doing voltage drop tests on battery cables, wiring to fuse blocks, main ground locations... If you do happen to catch this acting up I'd monitor B+ inputs to the BCM. There appears to be too many circuits involved to just be a BCM fault. There also could be other symptoms that weren't mentioned or noticed. That GDS2 report is displaying unusually…

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William Technician
West Virginia
William
   

Scott, I agree with your statement about voltage dropping the components, but I would have to disagree with your statement about to many circuits to be the BCM… and here is WHY: All of these systems in the first and second document receive the power mode from the BCM via the low speed gmlan or hardwire from BCM. Bill has codes from the following systems other than the BCM. - Steering Column…

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Thanks
Scott Owner
California
Scott
 

Hi William, I agree with the importance of the BCM as it is the PMM on this vehicle. I was taking into account the stalling, the remote starting that has occurred, and the erratic blower motor operation. As far as the radio, are you asking/telling because of the GDS2 report I posted? I'm rebuilding the differential on that and the only reason I posted that was the vehicle was convenient to…

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William Technician
West Virginia
William
   

Sorry for the confusion. No I did not take any of the information off your gds2 report I was only talking about bills report. I was stating the reason why all of his problems can be explained by the BCM and incorrect PMM operation… In my experience the most failed gm module is the BCM, but that is anecdotal. I only put so much so much weight on the bcm because of the discrete data signals…

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Lewis Technician
California
Lewis
 

I would start with the battery cables . Especially the ground cable

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Bill Owner/Technician
Michigan
Bill Update
 

I have rechecked BCM ground points this time with a second person shaking and pulling on the harness near the ground connections - Nothing changed. I have several leads at the BCM monitoring B+ inputs - not finding any loss of voltage at this point. I inspected the wire harness under the dash per Williams PIT document it's not pinched. At this point I am using this vehicle as my daily driver to…

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Victor Owner/Technician
Florida
Victor
 

Maybe it is time to call in an exorcist.

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Robert Owner/Technician
Virginia
Robert
 

The last one i had similar to this turned out to be pcm. Yes i know does not make sense.

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Bill Owner/Technician
Michigan
Bill Resolution
 

I replaced and programmed a new BCM. Vehicle has been back to the customer for 1 ½ weeks I followed up with them yesterday and so far so good / no issues have reoccurred. I will follow up if the vehicle returns.

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