[sgl944t]

Can anyone help me determine how to resolve this problem. I initally had code that the dealer was a shut-off valve replacement and I replaced it. The next code was P1123 Oxygen Sensor (MAS) and I tried using Brake Clean but now I get P123 which is 02 Sensor Circuit No Activity Detected Bank 1 Sensor 1. I am thinking to get a new MAS Sensor and see if that solves the problem. Any ideas would be appriciated.