Saying Hi and need some advice please

[RESQ-MYTECH]

Hi Louis and the gang from the otherside of the pond. My name is Marc and I am from the London/ Essex borders. Spoken to Louis a few times via email and now in the need of some assistance.
Here is the issue. Macbook Pro A1502 early 2015. Came to me with a broken screen and a booting issue. Replaced the screen with no problems. Booting issue is it will reach the log on screen but the mouse and keyboard were inoperative. Plug in a USB mouse and keyboard and I am able to navigate with the mouse, enter the password and enter the O/S with no issues. I can navigate around using both the USB mouse and keyboard with no problem except for the onboard mouse and keyboard are still inoperative. All though guaranteed by the customer the unit has never got wet ( and we know that sometimes this statement to be false), there is a small amound of corrosion on the I/O board the houses the HDMI/ SD/ USB ports. So this is what I have done thus far:-
Disconnected the joining ribbon from the logic board side that connects the I/O board to the logic board. No change on the keyboard and mouse, still inoperative.
Disconnect the mouse ribbon to eliminate that causing an issue. No change.
Connected a new keyboard. No change.
Removed the logic board and examined under a scope. There is no indiacation of any liquid ingress on the logic board what so ever. Not like the I/O board that does have some dull prob points.
Attached another battery of good origin ( saw this on one of your video's Louis). No change.
Checked pin 5 on the keyboard for voltage ( again seen on one of your video's). Voltage is there. You can power on with the power button with no issue, just other keys not working one at the log on screen.
Booted to another install of O/S ( tried el capitan/ sierra and high sierra) via USB hard drive and still the mouse and keyboard remain inoperative. Only way I could do this is with a USB keyboard plugged in as after power button is pressed the onboard keyboard the "option" key did not respond.
Followed a suggestion by a collegue to reset the SMC and NVRAM. I did a restart and using the USB keyboard reset the NVRAM which I did first and the keyboard and mouse were live. I could enter the password with the onboard keyboard and could navigate the O/S using the onboard mouse and keyboard with no issue. I did disconnect the USB keyboard before entering the password so I know it had no bearing on the onboard keyboard working.

Returned the Macbook to the customer, he got home and called me saying the keyboard and mouse were not working. He brought it back to me, lo and behold he was right. I had to reset the NVRAM again using an USB keyboard which got the mouse and keyboard working.I restarted the unit multiple times and powered off completly multiple times and on each boot the mouse and keyboard worked fine. Yesterday morning, he called again and said that he could not get the mouse and keyboard working. He brought it back, I did the NVRAM reset and they both worked and could get into the O/S without issue. I am not exagerating but over the course of yesterday I must have restarted/ power off and boot over 50 times and each and every boot was succesful where the mouse and keyboard worked fine. I did the last one at 5pm last night. Met up with the customer at 10pm, went to show it to him working and again the mouse and keyboard were inoperative. It would seem that a long power off period causes the NVRAM to have to be reset to enable the mouse and keyboard.

I have searched around on the net and the closest I have found to this issue is linked to filevault on el capitan. But upon reading the symptoms are not indicative of what I am experienceing.
Given that the mouse and keyboard both work after the NVRAM reset and all keys/ trackpad and click work OK fine, I feel confident in discounting the mousepad and keyboard as culprits, especially after connecting a new keyboard and having the same issue.

I am sorry for the long discription but want to give as much info as possible. Any ideas/ pointers on what the next step would be is greatfully received. Just a bit of background on me. I have been in the industry for 23yrs but only been doing Apple repairs for about 12 months, so I am pretty new to the repairing of Apple products. Most of what I have done above, effectivly would be the same course of diagnosis I would have done with a PC based unit, so I may be over looking something that you guys may say...." Do this!"

Thanks for taking the time to read this and hopefully I can get a resolve.
Marc

 

[ALB-Repairs]

most likely a trackpad cable failure. if the tpad cable fails the keyboard wont function correctly.

 

[RESQ-MYTECH]

Thanks for your answer ALB-Repairs. If I have disconnected the trackpad cable, would this not eliminate the trackpad as a cause? Even with it disconnected the keyboard fails to work.

 

[2informaticos]

Keyboard lines go to mainboard, information is coded and sent to trackpad circuitry, via I2C.
From there, keyboard information is re-coded and send to PCH, together with trackpad information.
Final communication is done via USB, before OSX charged.
If filevault is enable, on the password screen USB mode is still enabled.
After OSX charged, SPI mode communication is enabled.

So your test (disconnecting trackpad cable) leave both trackpad/keyboard inactive...

 

[RESQ-MYTECH]

Thank you for your reply 2imformaticos. I understand what your saying. Question I have is, if I power on, press and hold the option key I do not get the chance to choose a boot device, so the keyboard is not operating before even reaching the operating system. It goes straight to the logon screen. So if I disable filevault, would this (hopefully) resolve the issue?

 

[SMMRepair]

Just replace trackpad cable already. The keyboard isn't working because the trackpad cable is bad. Also possible the trackpad itself is bad, but super unlikely.

 

[2informaticos]

You should reach boot menu even witout SSD, so filevault is not involved...

Be sure your trackpad flex is OK.

 

[RESQ-MYTECH]

OK. so an update. Trackpad and trackpad cable changed..... no change. Filevault turned off. 10 hours to de-encypt the ssd... no change.

 

[RESQ-MYTECH]

Anyone? Should I say to the customer there is no repair possible and quote for a replacement logic board?

 

[Alan.L]

diode mode measurement on J4802 pin35 and pin37?

volage on PPVIN_S4_TPAD_FUSE ?
voltage on PP5V_S4_TPAD_F
voltage on PP3v3_S4?

 

[RESQ-MYTECH]

Hi Alan.L I will have to await for the customer to now bring it back. for the meantime I have lent him a bluetooth keyboard and mouse. I will update with the results ASAP. Thanks.

 

[RESQ-MYTECH]

Huh... well there you go. The customer took the A1502 back to the local Crapple store and they have taken it away for diagnostic, with an initial quote of just shy of £500 for the repair. The customer has given them authorization to just go ahead and repair the Macbook. I am sure there must of been some logical reason as to why this was happening, however, not having the Macbook back to try what Alan.L suggested, I will never know. Thanks to everyone that suggested things to try.

 

[RESQ-MYTECH]

Sorry to bring this to the top of the forum again but I got some more feedback from the customer earlier today. He took the Macbook back to Apple and they diagnosed the issue as a faulty trackpad cable, as did a few of you on here. He left it to be done, telling me that I didn't know what I was doing and he shouldn't have brought it to me in the first place... ( Hey Ho). Today he came in telling me Apple had charged him £487 to change the cable. WHAAAAAT! When I looked at the receipt he had been charged for a replacement logic board AND a cable. He appologized for what he had said to me and he left with us shaking hands. Thing is, it's still unclear as to what or where the fault lay... I supose now the board has gone we will never know. Thanks for the advice given.