4SNS/1/C0000008: TGOD--124

I have the same issue. In the end it turned out that the error refers to a dead graphic controller. It might be a massive failure that early 2011 MacBooks have - here there is the link to the article describing this issue http://bgr.com/2014/10/24/2011-macbook-pro-discrete-graphics-card-failure/

So, I'm afraid that anyone having this issue need to read carefully the article and the recommended actions.

Welcome to the Apple Support Communities

We can't access to the meaning of your error, but it seems like a sensor problem. Take the Mac to an Apple Store

bit_jammer is right. The T indicates a temperature sensor and G indicates it is on the graphics processing unit (GPU)