What does this mean? I have already replaced the O2 sensor and it still shows this code.
My car has an automatic transmission.
Hello. P0135 is the code for an oxygen sensor heater circuit malfunction, bank 1 sensor 1. If bank 1 sensor 1 oxygen sensor has been replaced, then it may be possible that the issue is with the wiring or connector that go to the sensor. Heated oxygen sensors use four wires, two for the oxygen sensor signal, and two for the heater circuit. I would test the wires of the oxygen sensor circuit to determine if there is proper voltage. If there is not, i would carefully examine the wiring and connector. A certified professional from YourMechanic can assist with diagnosis of the code by inspecting the car firsthand and pinpointing the underlying issue.