T3 TDI Waranty Question

I own a 2013 TDI Executive that I purchased in Octoboer of 2013. I know that the bumper to bumper warranty is over, but what about the powertrain warranty? I was under the assumption that the powertrain warranty for TDI's was much longer. I had an Oxygen Sensor and a NOX sensor go bad after the bumper to bumper warranty expired. I was told by the service adviser that they are not covered by the powertrain warranty, which surprised me. I held off on fixing them because I was sure that VW would eventually have to buy back my car. I ended up paying for the NOX sensor replacement becuase my AdBlue level was low and they could not reset the adblue level warning without replacing the sensor. I still help out on replacing the O2 sensor because I was sure VW would not be able to come up with a a fix. If I want to sell the car now, I will have to replace the O2 sensor.

Here are my questions:
How long is the Powertrain warranty?
Is the O2 sensor and the NOX sensor covered by the Powertrain warranty?