820-3476 shift keys dont work

[Gannons3]

All other keys but the shift keys work, I replaced the keyboard but they still do not work, computer was liquid damaged

 

[smiba]

Does both the left and right shift not work?

Anyways inspect keyboard connector for corrosion and check continuity for all WS_KBD signals to the U4801 chip
Already tried booting into a OS from USB to verify its not a software issue? (Pro tip: In ASD OS there is a keyboard test)

 

[Gannons3]

yes its both shift keys, also ive never used asd before so no idea which version to use

 

[smiba]

My bad, 820-3476 is the macbook pro 13" late 2013 right? Apple uses ASD2 for that which is not available for unauthorized stores

So like I said check the connector and WS_KBD signals. If thats all looking alright boot into something like Internet Recovery and see if you can use the shift key in there. Otherwise U4801 might be damaged but this pretty much never happens

 

[Gannons3]

also forgot to mention that I had the customer try to do an smc reset just to see if it would work outside the os. and it didnt work

 

[dukefawks]

Left shift and right shift are 2 completely different things. Right shift is part of the keyboard matrix along with all the other keys. Left shift is part of the SMC reset circuit. It seems unlikely both keys are not working.

 

[Gannons3]

customer claims both shift keys arent working, ive yet to get the computer back though, ill update when i get it

 

[Gannons3]

okay so the customer finally brought the computer back, and it seems that both shift keys don't work along with the left option key, I had continuity between the connector and u4801. I tried another keyboard and that had the same results. Usb keyboard works fine. after using the usb keyboard the rest of the keys started misbehaving, not showing the correct character or doing nothing. so i replaced u4801. After the replacement absolutely nothing has changed, so i have no idea how to proceed.

 

[dukefawks]

Check if left SHIFT, OPTION and CONTROL are not functioning

 

[Gannons3]

they're not functioning no

 

[Gannons3]

i also had continuity to and from U4850 for those keys, and replaced U4850, didnt solve the issue

 

[dukefawks]

That means no 3V42 to the keyboard on pin 4. Probably a bad connector but could be trace to the connector.

 

[Gannons3]

i do get 3v42 to pin 4 on the connector

 

[dukefawks]

Pin 1 2 and 3 should come high when the corresponding key is pressed. Usually corroded pin inside the connector or bad keyboard.

 

[Gannons3]

does the computer need to be on to run high or will it do it while off?

 

[dukefawks]

Can be off but needs to have 3V42 present so either battery or adapter needs connected.