No Tach After Harmonic Balancer Replacement

I have a 97 Olds Silhouette with about 170k miles in it. The crank shaft pulley/harmonic balancer was gong bad. The Outer ring was sliding out, eating up the serpentine belt.

I replaced the pulley with a new after market one from Napa but when I restarted the car, the tach. Did not respond and the service engine light came on. Might I have damaged the sensor behind the pulley or is there something I need to do to reset the computer? Thanks!