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    #1

    Macbook Pro 13" PBus issue

    Hi Guys!
    Im new at this forum and it really looks promising so far.
    I am an ACMT for the last couple of years and just now i started to study the world of component repairs.

    I have this Macbook Pro 13" A1278 (MacBookPro8,1) logicboard that runs very slow because of high CPU usage, in activity monitor i can see the Kernel_task on 380%+- all the time.
    I then tested the MLB with another known good Topcase and the issue persist, which points to faulty logicboard.
    I run Apple Diagnostic Test (ASD) and failed on Sensor-Voltage (VP0R)--PBus (Test 1)- Sensor is reading below the low limit.
    I then read about PBus and found that it belong to the battery controller and in the ASD test results guide i can see that the VP0R is the PBus rail which i don't know what is (yet).
    My question is which one is the VP0R? and is it possible to fix it?
    I have an SMD rework machine (Aoyue 968A) and ready to start actually using it..
    As i said before my knowledge about components is not big at all but I'm more then willing to gain some knowledge and this forum look like the right place to do so (:
    Last edited by davis12; 11-05-2012, 05:10 AM.
    Tags: None
    #2
    Re: Macbook Pro 13" PBus issue

    am i doing somthing wrong with this thread or there is not many that know about apple logicboards??

    Comment

      #3
      Re: Macbook Pro 13" PBus issue

      You say PBus belongs to the battery controller. Does the issue persist when you remove the battery?

      I do not, and have never owned a Macbook (too expensive, plus i hate Linux and OSX fonts with a passion), but i browse the Apple support forums sometimes, and i've noticed lots of people with kernel_task issues. The solutions were of the most diverse, in fact, i don't even know if i read of two machines that got fixed the exact same way.

      Edit: Forgot to add, what are the temperatures, and how fast does the fan run? It can also point to overheating.
      Last edited by Th3_uN1Qu3; 11-06-2012, 04:59 PM.
      Originally posted by PeteS in CA
      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
      A working TV? How boring!

      Comment

        #4
        Re: Macbook Pro 13" PBus issue

        Spot on! when i remove the battery and restart the machine no issues at all and the killer Kernel_task is gone..
        I also testet with a known good battery and the kernel_task is back to life but no high temp or high spinning fan, quit as the sea but very high CPU usage.
        Any ideas?
        I can upload pictures of my logicboard if needed.

        Originally posted by Th3_uN1Qu3 View Post
        You say PBus belongs to the battery controller. Does the issue persist when you remove the battery?

        I do not, and have never owned a Macbook (too expensive, plus i hate Linux and OSX fonts with a passion), but i browse the Apple support forums sometimes, and i've noticed lots of people with kernel_task issues. The solutions were of the most diverse, in fact, i don't even know if i read of two machines that got fixed the exact same way.

        Edit: Forgot to add, what are the temperatures, and how fast does the fan run? It can also point to overheating.

        Comment

          #5
          Re: Macbook Pro 13" PBus issue

          This sounds like a hardware issue but you may be able to work around it.

          As far as my understanding of OSX goes, kernel_task runs a bunch of kernel extensions under it, kinda like svchost.exe does on Windows machines. There are software tools available which break down kernel_task into its child processes, and show you what each of them does and the resources they use. You'll have to google it but i'm sure you'll find these tools easily. That way you can pinpoint the resource usage to a single process, and see what can be done about it.

          I understand the machine does run on battery, right? Just that it's slow with high CPU.
          Originally posted by PeteS in CA
          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
          A working TV? How boring!

          Comment

            #6
            Re: Macbook Pro 13" PBus issue

            your machine required the factory default settings

            Comment

              #7
              Re: Macbook Pro 13" PBus issue

              Yes it does run on battery but thats also what provoke the kernel_task/CPU usage.
              The strange thing about all this is that one thing is that i know it is a sensor VP0R as the Apple Service Diagnostic points to and i know that it related battery and fixed when the battery removed but i also found out that there is no issue with the kernel_task and the CPU usage when i boot into safe mode..
              So is it software or hardware issue? is it both? i obviously need to find out which kext is responsible the reporting of faulty sensor which cause the high CPU usage and delete it in.
              Also if i only knew where is this VP0R sensor located on the board and try to replace it but as i mentioned before i don't know that much on components level or reading those diagrams (:yet)

              Originally posted by Th3_uN1Qu3 View Post
              This sounds like a hardware issue but you may be able to work around it.

              As far as my understanding of OSX goes, kernel_task runs a bunch of kernel extensions under it, kinda like svchost.exe does on Windows machines. There are software tools available which break down kernel_task into its child processes, and show you what each of them does and the resources they use. You'll have to google it but i'm sure you'll find these tools easily. That way you can pinpoint the resource usage to a single process, and see what can be done about it.

              I understand the machine does run on battery, right? Just that it's slow with high CPU.
              Last edited by davis12; 11-08-2012, 08:51 AM.

              Comment

                #8
                Re: Macbook Pro 13" PBus issue

                a
                Last edited by davis12; 11-08-2012, 09:03 AM.

                Comment

                  #9
                  Re: Macbook Pro 13" PBus issue

                  Originally posted by Abdul Rehman View Post
                  your machine required the factory default settings
                  Do you mean clean install??
                  it does the same thing with extern system with 10.7, and the system is a fresh copy of mountain lion 10.8.

                  Comment

                    #10
                    Re: Macbook Pro 13" PBus issue

                    Hi........I have a macbookpro A1278 model and at one moment when i as working plugged in with power, suddenly the fan started running at a high speed,more heat at the bottom and the machine got switched off .Before that my battery was in a good condition. After this instance when i plug in the power adapter to my MBP the green light is not glowing and not charging the battery.The battery indicator is not at all working.So.emphatically my MBP behaves like a brick.No response from power button also. Someone plese suggest me what would be the problem inside the Machine.

                    Comment

                      #11
                      Re: Macbook Pro 13" PBus issue

                      Originally posted by davis12 View Post
                      Do you mean clean install??
                      it does the same thing with extern system with 10.7, and the system is a fresh copy of mountain lion 10.8.
                      Im having this same issue. Can you give us a little follow up on how your situation turned out?

                      Comment

                        #12
                        Re: Macbook Pro 13" PBus issue

                        hello,
                        i have a macbook1278 820-2936 same problem when u use the adapter is works perfect and when u run only in battery the cpu usage hig the trakpad gets jittery and becomes to slow the machine. i have changed the smc chip battery.
                        pls does anyone know where to look for the problem
                        thanks

                        Comment

                          #13
                          Re: Macbook Pro 13" PBus issue

                          Check area q5300 pbus voltage sense.

                          Comment

                            #14
                            Re: Macbook Pro 13" PBus issue

                            So have you tried this https://support.apple.com/en-us/HT201295

                            Comment

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