How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Hal Your Own Question

Hal, Chevy Master Tech
Category: Chevy
Satisfied Customers: 1029
Experience:  ASE and Chevy Master , 31yr Dealership exp,
Type Your Chevy Question Here...
Hal is online now
A new question is answered every 9 seconds

I have a 2001 GMC Yukon Denali. It has longstanding intermittent

Customer Question

I have a 2001 GMC Yukon Denali. It has longstanding intermittent electrical issues. The symptoms are: Several gauges in the dash go to their "off" position intermittently including: fuel gauge, temperature gauge, battery voltage. In addition, OnStar LED will show Red. I purchased an OBDII scanner, which doesn't work when this happens.

I believe this is an issue with the bus between the various modules (PCM, BCM, Air Bag Module, OnStar module). I was able to confirm this by isolating modules via Splice Pack 205, where the modules connect to each other. The Bus (or level-2 communication I think they called it) would be locked up until I disconnected the PCM and the BCM from everything. After I disconnect these two, and connect everything back together, the system would operate correctly. I suspect either the BCM or PCM. I have had the BCM reprogrammed at a repair shop, which cost me $100, didn’t fix the issue.
What do you recommend? Replace BCM? PCM? Something Else?
Submitted: 5 years ago.
Category: Chevy
Expert:  Hal replied 5 years ago.

Hi my name isXXXXX

I feel your frustration with this kind of concern. You are correct, the concern is with the Class 2 communication. Unfortunately this is one of the most difficult concerns to Isolate.

Any one of the modules on the class 2 line can be the culprit. You have a good start in going to splice pack 205 , and isolating it down to a BCM or PCM.

Reprograming does not correct a hardware issue with a module witch is usually the case in these matters.

If I were at this point I would check or rerun the communication line to the modules first.

If that did not correct and I did not find a definite short to ground, Next make sure there are no after market devices hooked in any where. Connections to data sources powers and grounds to modules will make them do weird things. But I don't think that is your concern here.

I would replace the BCM they have had more issues than the PCM. Plus the BCM is responsible for the body functions that your having troubles with.

Look around the left inner fender for the most likely spot for the communication line to be shorted that goes to ECM. It is most exposed and I have found allot of problems in that area.

Hope this is the info you were looking for. HAL

Customer: replied 5 years ago.
I will accept the answer, but just a few more points of clarification please. For looking for the most likely spot for the communication line to be shorted, can you provide a bit more detail in terms of where to look? Do I just find the ECM, then the harness that feeds the ECM and look for a short? If I find a short or bad harness, I guess that will need to be replaced first?

Expert:  Hal replied 5 years ago.

Yes I can thats not a problem.

The ECM should be located on the front left inner fender. Follow the harness up to the under hood fuse block. This is where I find most wiring issues. The harness will go under the UHFB and into the vehicle though the pass through grommet lower left of fire wall. It comes into the vehicle and up and over the emergency brake pedal. ( this is another location to inspect the harness. The BCM should be left of the steering column, or just below the column.

All you need to do is make sure the harness is not shorted to ground. Go to the splice pack as you have already done. find the wire to the ECM and BCM. Unhook the BCM and ECM and ohm out the wire. If you have continuity to ground then the circuit is shorted. If not then it is the module. This is exactly how I have to diagnose these type of problems.

Hears the catch. the condition MUST BE PRESENT to find it. As i stated before these types of concerns are very difficult to isolate unless they are hard failures.

If you need wire colors or terminal locations Let me know.

PS the reason I said replace the data circuit is because if it is shorted , it is sometimes easier to just replace the wire that it is to locate the short. At least it is for me.

Hope this info is what your looking for.

Hal, Chevy Master Tech
Category: Chevy
Satisfied Customers: 1029
Experience: ASE and Chevy Master , 31yr Dealership exp,
Hal and 7 other Chevy Specialists are ready to help you
Customer: replied 5 years ago.
Thanks, XXXXX XXXXX very helpful.
Expert:  Hal replied 5 years ago.

Your welcome, and thank you for using just answer.

Thanks again Hal

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
< Last | Next >
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland

Meet The Experts:

  • Tim's Auto Repair


    Satisfied Customers:

    Have owned a repair shop for 25 yrs.
< Last | Next >
  • Tim's Auto Repair's Avatar

    Tim's Auto Repair


    Satisfied Customers:

    Have owned a repair shop for 25 yrs.
  • Dave Nova's Avatar

    Dave Nova

    Chevrolet Technician

    Satisfied Customers:

    ASE Master Certification. GM World Class Certification
  • Gary's Avatar


    Chevy Technician

    Satisfied Customers:

    15 years GM master tech
  • John's Avatar


    Master A.S.E Automotive technician

    Satisfied Customers:

    A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
  • Don 'Mo Lurch''s Avatar

    Don 'Mo Lurch'

    Auto Mech / Electronics

    Satisfied Customers:

    Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.
  • Neal's Avatar


    Chevy Mechanic

    Satisfied Customers:

    Shop Owner and Mechanic on multiple makes.
  • Ron Z.'s Avatar

    Ron Z.

    - Chevy Tech -

    Satisfied Customers:

    18+yrs experience. State Inspector and Chevy Diagnostics
Chat Now With A Chevy Mechanic
owner/service tech
861 Satisfied Customers
ASE and Chevy Master , 31yr Dealership exp,