Trackpad motion only works in AHT and Startup Volume selection (SOLVED)

[artaslove]

Hello!

I was recently handed a no-signs-of-life macbook air 13" early 2015. No light on the magsafe adapter, no booting, etc. After a bit of investigation I discovered the IO board was not sending any voltage at all to the logic board. I ordered a replacement, installed it and voilà, power was back.

There was still a problem with codes PFM006 and PPN001 so I investigated a bit further and found evidence of possible spillage around the trackpad. I gave it a very good cleaning and cleared the codes.

Now it's at ADP000 - No trouble found. But there is still one problem. The trackpad works in AHT and during startup disk selection, but as soon as macOS is at the login screen or Recovery is loaded it stops registering any motion from the trackpad. Clicking works if I position the cursor with an external mouse. SMC and NVRAM has already been reset. The problem persists in a fresh user profile. Safe Boot doesn't make a difference.

Has anyone else encountered this problem? It's running 10.12.6

 

[artaslove]

Reinstalling Sierra doesn't solve this problem. I've got another trackpad on order, seeing as there was spillage/corrosion on the old unit. Perhaps the basic touchpad driver during startup disk selection does not initialize all aspects of the touchpad driver in use in the OS.

 

[artaslove]

Touchpad motion works using linux as well :/

Hmmm.

 

[artaslove]

This problem was finally fixed by replacing both the trackpad and the trackpad cable.