A NOx sensor protection system includes a flow control device forming an internal chamber with exhaust and shield gas ports and a NOx sensor. The flow control device is configured to selectively allow a flow of exhaust from an exhaust pipe to the NOx sensor when an internal combustion engine is operated with a first fuel, and to selectively direct shield gas from the shield gas port at an angle of 135° to 180° to the NOx sensor to inhibit the flow of exhaust from the exhaust pipe to the NOx sensor when the engine is operated with a second fuel.