Posted athread yesterday regarding difficulty in starting when hot. Responses indicated it was likely O2 sensor. (Thanks) The initial code indication was the front crank sensor and they wanted $197 to replace it. The mechanic is now telling me the code indicates it is the NOx sensor and wants $744 to replace it. That seems a little extreme. It took him 2 days to figure this out and I'm not sure I believe him. Is he trying to rip me off?

 

A knock sensor shouldn't really cause hard starting. This code is sometimes thrown with other codes and tends to go away when the other problem is fixed. If it is bad, they quoted $744 because the manuals say to remove the intake manifold. If you have small hands you can change it yourself. The sensor itself is only like $120.