As a professional diesel tech with Deere and Cat, I've never heard of anyone cleaning a NOx sensor. I certainly understand your need for a better solution but I don't think cleaning is going to be effective. For one, the downstream NOx is mounted at the tailpipe outlet where there is zero particulate matter to plug it up. It's going to be mounted in a location with a pretty remarkably clean air flow. It's not like an oxygen sensor that is exposed to soot. Second, there is a heater inside the NOx sensor that is used to get that internal temp up to the 2000 deg F level that it needs to operate. That makes it sensitive to cleaning chemicals and depending on the failure mode of your sensor, cleaning isn't going to do anything for ya if the internal heating element is damaged. If it were me, I would avoid buying Chinese, avoid buying from dealership. FCP OEM branded might be a good bet.