The P0155 indicates a problem in the heater circuit for the upstream firewall side sensor. If the sensor has been replaced for this exact code, then the sensor is not likely the problem. Most likely a wiring harness issue.

The P1151 code is for the OTHER upstream sensor.

Steve

98 Contour SE Sport 2.5 Duratec ATX The wifey's car 89 Taurus SHO - 246K miles 94 SHO ATX - 190K 1997 F-150 5.4L ATX - The Workhorse 150K. ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!