Got a rather strange problem with my 2006 X type in that it is getting a knock sensor 2 low voltage error. The car goes into limp mode and doesn't want to run above 3,000 RPM. What's strange is I can clear the code and drive her say 100 miles and the check engine light never comes on. But if I stop the engine then start her again there it is, knock sensor 2 error. Also, during the winter months when it is cold I can reset the code and it doesn't come back until the weather starts getting warm again. One bad thing here in Kansas is that our premium gas has 10% ethanol in it. Any ideas on what might be causing this since it is so intermittent?

 

By law many codes are 2-trip so cannot flag until you turn the car off as you describe, even though the fault is there. It's a well-intentioned law which works well almost all the time but does in rare cases lead to anomalies as in your post.

Fix it!