I have an 2000 Z-28 stock, my ses light came on when i stepped on the gas to pass an 18 wheeler on the highway. I got it checked and it came back w/ bank 1 o2 sensor and nock sensor. The guy asked if i had any trouble starting the car and i said no. Then he told me my harmonic balancer might be off and throws the ses for the nock sensor. Is this true? Would I have to replace the harmonic balancer?

Thanks in advanced.