Chosen Solution

So, full description of the problem first: When any disk in any mode is booted up on my MBP, the Z key doesn’t function. However, when it’s first turned on, when you first hit a key, it always types Z first, unless you hit the Z key first, then it just keeps typing Z like your holding it down until you hit another key. This effects my startup commands as well, so far all I can do is an SMC reset, go into single-user, and disk recovery, but that’s it. So! Where it gets really weird is what I’ve tried so far. To date, I’ve: Reset SMC and NVRAM (several times, NVRAM from single-user)Swapped out multiple keyboardsReplaced the Trackpad cable (just in case)Put in a new disk and installed a completely fresh copy of Mojave, then tried Mavericks for kicks, just in case.Stuck another disk in that was installed with OSX from a completely different early 2015, one with a working Z key.Checked and messed with pretty much every computer settings file that has to do with a keyboard At this point I’m at a loss. There was no liquid damage on the device, and no other damage. I really don’t want to replace the mobo, and I’m down to solder or replace anything on that board to get this working, but if it was a trace that failed, I would assume at least that more than 1 key would be effected, since they are grouped, save for left bottom 3 and caps lock. I am officially out of ideas. Help.

I understand you don’t like the idea, but after all that parts replacing and software resetting, I’m afraid there’s nothing left except a logic board side failure. The IC taking care of keyboard inputs seems to be your first and only candidate for replacement to fix the issue.

Pop the cap off the Z key and see what sticky stuff is holding the key depressed and clean it off. Wet your cleaning cloth lightly first. Never spay any cleaner directly onto your machine. Next, try resetting the PMU/SMC. Shut down your MBP, plug in the power cord, hold down on the left hand side of the keyboard, shift, control, option and the power key all together. Hold ’em down for about 50 seconds, then release ’em, and then press the power key…also holding down Apple, Option P and R keys for 3 chimes as the MPB is booting up may help you…. check to see what country your keyboard is set to –which should be at the top of the screen…looks like it could be Czech or Polish or Serbian….,.