1999 Hyundai Sonata now get code 1154

It's been a while since I 've been back to this forum. My previous problems were eliminated by replacing CPS trouble code pointed to this one and replacing spark plugs and plug wires again trouble code helped this one (misfire on cylinder 1). I now get code 1154. I removed the bank 2 (closest to radiator) sensor 1 (closest to exhaust manifold) and cleaned it with carburetor cleaner and heated it. Code cleared by battery disconnect. Code reappears after about fifteen miles of drive time. Should I replace the sensor or should I look for some other problem causing this? The car runs fine and strong. Also, can you tell me how to get at the windshield washer pump motor? The HMA service website has nothing on this. Thanks again for all your help.