Late 2013 rMBP keeps randomly shutting down...

[Molson1020]

Hey guys, can anyone help me out with this?

I have a late 2013 rMBP 15" and as of recently, it keeps randomly shutting down. It started when I updated to El Capitan a few weeks ago, but I have since used Time Machine to re-load Yosemite, but the issue is still occurring. I don't think its a kernel panic because I don't get the typical Kernal Panic screen, it just goes straight to black.

I have noticed it only happening when my laptop is on Wifi. When i am at work and plugged into my Thunderbolt monitor, it never crashes. However when I am off the monitor and using Wifi, it's occurring all the time (at least every 5-20 minutes). I have tried resetting the PRAM, SMC and have done a Repair Disk Permissions.

Does anyone know what might be causing this or has any experienced anything similar?

 

[Bending Pixels]

Have you run a hardware diagnostics (reboot and hold down the D key while plugged in) to see if there is an issue?

 

[Molson1020]

Have you run a hardware diagnostics (reboot and hold down the D key while plugged in) to see if there is an issue?

I did run a diagnostics. It said that my battery needed service. It's weird though, as these shutdowns happen when my Macbook is plugged into my power cord... however they don't happen when its plugged into my Thunderbolt monitor.