A few days ago, I encountered an issue which seems to be common among mid-2009 MBPs: one of the RAM (in slot 1) is not recognized anymore. Or, sometimes it is recognized, but after sleep and wake up, the computer freezes and impossible to recover but force power off.
It turns out this is a common issue in this model. See the discussion in this thread and this thread. In the following, I am going to present my temporary fix for this problem. For those of you that still want to stick to the old MBP, the fix shall last for a while. But I do recomend you backup all the files and prepare to migrate some day soon.
As I suggested in my reply, this may due to a RAM slot degradation. My guess is, the RAM slot cannot align the RAM to a correct contact positions any more. Precisely, see the post image above. Notice that the two clips on the left and right are used to hold the rams in a horizontal position, otherwise they will bend upwards. I took a close look at those clips and found that the plastic wore out and cannot hold them as original. I don't have great ways to fix them, so I just cropped some papers and insert them between the RAMs and the back edges on the body, hoping they can help tucking the RAMs.
As I am fixing it, I accidentally broke the left holder. So I have to customized a plastic holder and stuck it with the logic board to hold the inner ram (slot 1).
To verify my theory, I then taped a padding at the corresponding RAM position in the back cover:
And they look like the following before I close:
Note that you have to screw it real tight to create the pressure such that the RAM is aligned. That said, there will be a 'bump' at that position, and will easily cause scratch. So I use an apple sticker to cover my ass:
This method worked for me, well, at 99% of the time. Sometimes after sleep, the MBP still won't wake up. I notice that this usually due to running the MBP for a long time, and it's hot inside. Nevertheless, this is the best solution I can come up with by now. If you have any other cheap solution that does not require replacing the logic board, please let me know in the comments.
Finally, Zach Clawson created a dedicated page for this issue, which lists lots of reference and provides explanation to it. Make sure you check it out if you have encountered similar issue.
There are other common issues for this model, and they can be easily fixed. See my following posts:
If you have similar experience, do not hesitate to let me know. If you find my instruction helpful, leave a comment and share it!