I'm trying to fix my o2 sensor problem on my 98 Tacoma. it started a while back when the check engine light came on. the code was po125,po130 and po133. I checked the o2 sensor with meter and it checked out good. then I checked the wiring harness with meter and it showed it was getting 12 volts but it was not getting a ground. I though that I could tie a wire into the heater ground on sensor and ground it to the truck frame and the ground would be ok. that did not work and not I'm getting code po1135 saying ground fault. question is could the po125 be the main problem, I changed the thermostat and that did not help. Could it be the temp sensor? could someone steer me in the right direction? thank you