Really weird issue

Got a weird one here. Mid 2012 13 inch air. i7 8gb ram. If you turn it on it powers up chimes and then switches off at the Apple logo screen.

However if I hold a key down any key it boots up normally. If I let go of the key it will stay on for 30 secs then turn off.

No water damage. Apple diagnostics say no issues found. Any ideas

Thanks in advance.

 

it cannot see the battery in OSX system report which is weird, it boots with the battery unplugged as long as i hold a key. I am leaning towards either the SMC firmware has got corrupted or a logic board issue.

it starts out dark and i have to turn the brightness up within OSX once i am in. so i think that somehow the SMC has lost a lot of info.

whats weird is as long as a key is held down it works perfectly

 

if i am not holding a key it will just shutdown regardless if the battery is plugged in or not. It makes no difference what key is held down as long as one is.

i have been using the fn key boots into OSX and works just fine until i take my finger off the key and then it shuts down. never seen or heard of this before. I repair Macs for a living and this one has me baffled LOL

 

worth a shot, will give it a go

 

will do, i got given it for free as they could not even get it into OSX. with the specs on this i would love to fix it and use it as my daily driver as my Pro is getting a little long in the tooth lol

 

Yep unplugged the keyboard cable and boom no more issues.

 

if i remove the ribbon cable, battery shows and is charging and it boots no issue. Plug the cable back in it either does the switch off to half the keyboard does not work. ordered a 30 buck replacement

 

whole top case part with keyboard

 

ebay