I have been getting codes 42-43. Pretty much traced the codes back to the knock sensor either being faulty or the connector being loose. The blazer is running fine at all ranges, what is troubling me is after replacing the CPI unit I got 17 MPG, from 14 prior to the exchange. This tank (second) since the new CPI,I got 13 MPG. The only thing I have noticed is the service engine with codes 42 and 43 which will go away if I jiggle the connector on the knock sensor. They will come back during normal driving I suspect from either road vibration or potholes.

My question is: Can the faulty sensor send so many false triggers that it could impact the MPG.

 

So here's what the manual says about the ESC and knock sensor....

"Loss of the ESC signal to the ECM would cause the ECM to constantly retard the EST. This could result in sluggish performance and cause a code 43 to set"

It also says, a code 43 indicates the ECM is receiving less 6 volts for a 4 second period. It's not clear but i assume they mean the ECM is not receiving a signal from the knock sensor or ESC.

I am also wondering how much 10% ethanol impacts the ESC

 

I cleared all the codes today and all seems good. No 42-43 showing back up. I did wrap the connector a little tighter around the drivers side sensor, also looked and found the back side sensor and it was all tight. So, it seems at the least I'll be replacing the connector to the drivers sensor when I get some extra time. Still not sure if this had anything to do with my poor MPG but now that the connection is solid guess time will tell.