02 Chevy Silverado 4.8 front timing seal replacement?

[flashgordon]

I changed the front timing seal. When I removed the harmonic balance pulley I noticed there was not a key way. I did not know this prior to removing it so I did not mark anything. When finished replacing the seal I just reinstalled it. I then cleaned the engine. I am now getting service engine codes for low voltage on both of the knock sensors. Did I install the balancer wrong or did I get the knock sensors wet some how.