I have an August-2013 13" retina MBP with a SanDisk 256GB SDD. I've been tolerating a noisy fan for the last few weeks. Today I ran Apple Diagnostics & got this error code: 4SNS/1/40000001:VP0R-0.000 I chatted with Apple Customer care. They got me to do an SMC reset & run extended diagnostics. The same error message still appeared. Apple told me it may be a temperature sensor issue, causing the fan to run at incorrect speeds. They told me to take my MBP to the service center. Actually, my MBP is running ok, other than the noisy fan (and shorter battery life). I also saw on these threads issues with SanDisk's SDD. I want to continue using my MBP, and only suffer the inconvenience of taking it to the service center if the problem worsens. Whatever it is, I'll get it fixed before the warranty expires. Just want to know if I'll void the warranty if I don't do what Apple tells me to do, and something drastic happens.