Recently, my mid 2009 MBP (Model A1278) fails to recognize the hard drive. My first bet was another disk failure on me, but it was not the case. I took down the hard drive and put it to a mobile hard drive case and it can be read smoothly.
Luckily, the solution is simple, just go ahead and purchase a replacement cable and replace it. iFixit has a very detailed illustrated document on the procedures. However, Amazon has a cheaper option, and it works fine for me. I didn’t test the infra-red though, since I never and not plan to use it.
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!