i have a late model 99 with a 5.3 and the check engine light came on i had the codes ran and it came up as the knock censer. But my motor has no knock to it at all, so ether i need a new one or it is lose and i have no clue where it is located.

 

The knock sensors are recessed in the valley cover under the intake manifold. If water gets in there they will corrode the sensors and screw the readings up. That would be my guess....it's a pretty common problem especially if you powerwash your engine.

If you replace them, run some silicone around the rubber seals.

 

what most likely happened is over the time of your trucks existence water has gotten into the foam padding they put over the knock sensors and they are completely rusted out, so now they aren't sending the signal to the pcm as they should. you'll have to pull the intake manifold and replace them. like yankee said put some sort of sealant on them when you replace them.

 

well i haven't have the truck for too long and i bought it off of an old man, the check engine light came on a few hours after i pressure washed the motor for the first time and haven done it since

 

If it cleared and doesn't do it anymore you should be fine.

 

yeah if the light's off you're good.