MacBook very slow and power button pressed for 5 seconds to turn on

Hello everybody,

This is my first post on iFixit. Most of the problems that I had with my devices were solved with answers founded in this forum. So thank you very much!

But the current problem I was unable to solve it. Despite the weeks of searching on the internet I couldn’t find an exact solution for my problem or due to lack of information. So I decide to try writing it here. So here it goes:

My macbook is a pro 13” late 2011 with RAM changed from 4 GB to 8 GB (4GB each) and 500 GB HD to 500 GB SSD.

The macbook only starts when a I press the power button for more than 5 seconds. When pushing the button quickly the fans turn on and I can hear the beginning of the boot and then it turns off.

After a long time on the loading screen, the macbook works but extremely slow. The kernel activity on task manager is on 400%!

I’ve already tried:

-Removing battery

-Reseting NVRAM

-Reseting SMC

-Reinstalling OS

And nothing of the above worked. The closest of getting it fixed was formating the SSD through other mac and installing the OS original from factory. But, the app store didn’t let me upgrade to the latest version that was allowed to my model and kept sending me an error message.

Shortly after, the first problems of slowlyness and 5sec button pressed returned.

That last thing I did was a Apple Hardware Test that found the following error:

4SNS/1/40000000: IB0R-9.166

I think it is related to a battery problem. After some searching about this error I’ve found many forums saying that it’s a problem with some corroded capacitors (which I was unable to identify because I don’t have the schematics of the board).

My questions are:

1- Where I can get the schematics for the motherboard?

2- If it is the battery, what tests should I do in order to check the health of it?

3- Any suggestions of what should I do next?

Thanks in advance.