[Nervous wreck]

I have 2011 Gmc 3500 6.6 duramax have a po546 code where is this sensor located and do you have pictures

 

[jeenglis]

I believe this is the temperature sensor located in the down pipe near the turbo. Standing in front of the engine, sensor is located left side of the turbo near the clamp.

 

[Ron Nielson]

This is from my 2008 model:
Circuit/System Description

The exhaust gas temperature (EGT) sensors are variable resistors that measure the temperature of the exhaust at the inlet and outlet of the diesel particulate filter (DPF).