The most common failure point is the NOx sensor. This is a vital but complicated piece of equipment that can cost between $1,800-$2,100 to replace. There are other things that can go wrong.

The knock sensor is a complete pain in the tailgate to replace. You have to remove the air plenum, the intake manifold, the timing belt and lots of other stuff to get at it.

Furthermore, with use of the virtual sensor, the engine control strategy can be directly based on NOx emission data, resulting in reduced response time and improved transient emission control. This ...