2003 Hyundai Accent Replaced 0xygen sensor 3 Times Not Fixe

I have a 2003 Hyundai Accent with a 16 DOHC 4 cylinder engine. My check engine light came on a few months ago and I had the codes read. The codes were p0030 and p0133. They came up as being a possible bad oxygen sensor (front position before the catalytic converter) or a bad electrical connection. I purchased a Bosch OE Type sensor from auto zone, put it in, disconnect the battery to reset the check engine light, but after driving the car for 100 miles the light came back on. I had the codes read and the same codes came up. I took the O2 sensor back to auto zone and asked for a new one. They gave me a new Bosch OE type sensor and I installed it, but the light came on again. So I order an Hyundai OEM Factory Oxygen Sensor, installed it, and the same story. The check engine light came back on. In order to beat a dead horse I figured I would try a universal sensor. I bought a Denso 4 wire O2 sensor, installed it, cleaned and put electrical grease on the connections, but I am still getting the same codes. What in the world could possibly be wrong with my car. I took it to a ASE mechanic and he told me that my oxygen sensor was bad. I told him I already replaced it and he said that he would have to start by replacing it again and then figuring it from there. I have to pass emissions in 1 month. P.S. I also replaced my 2nd bank oxygen sensor with a factory OEM sensor from Hyundai. Any help or advice would be greatly appreciated!