i helped a friend of mine this past weekend that had a check engine error code. i found out it was the the knock sensor so i changed it out. i reset the computer and it was fine. the next day he goes to drive the car and the light comes back 20 mins in to the drive. what would cause this??

also he has a 1999 honda accord 4 cyl

 

Knock sensor code doesnt mean that sensor is broken, it means its working and you are detonating knocking or pinging. Start with general check up of plugs and wires and fuel filter. Something is either dirty or timing is off.

 

well i can say that the one we changed out was bad cause it was in 2 pieces lol. but i guess now it could be somethings else. Is there is a way i can check the new sensor is working right??

 

well that changes things lol. not sure but i would just assume its new and working....and in one piece.

Still perform basic tune up. if that sensor was neglected like that, Id imagine the belts and plugs are too

 

Check that the connections are good at the sensor connector first.

 

well according to my friend the plugs are new. belts he cant remember. as for the plug to the sensor he took it off and cleaned it out with air compressor to make sure and its still acting up. so i am not sure it can be. is there a specific voltage supose to come out of the sensor maybe i can check that?