Air/Fuel Ratio Sensor Heater Circuit Malfunction - P1155 Code - General
Air/Fuel Ratio Sensor Heater Circuit Malfunction - Bank 2, Sensor 1
OBD-II code P1155 represents a malfunction in the air/fuel sensor heater circuit for bank 2, sensor 1.
The air/fuel ratio sensor on your vehicle has to reach a particular operating temperature to produce accurate voltage signals. It needs to reach a minimum of 1200 degrees Fahrenheit before this can happen, and the sooner it reaches the operating range, the faster the sensor will be able to send accurate readings to the engine control module, or ECM.
In order to reach the proper operating temp, there is a built-in heater element as a part of the air/fuel ratio sensor. The ECM controls the air/fuel ratio sensor heater using signals received from the engine coolant temperature as well as the engine load. Voltage signals gathered through the heater element circuit are monitored and read by the ECM to determine the state of the circuit by comparing the voltage to factory specifications.
If there is a problem detecting the signal, the code P1155 will be triggered. When the code is prompted by a fault in this system, it will illuminate an SES or check engine light on your dash.
Much of the time, the trouble code P1155 is a result of these problems:
- Faulty air/fuel ratio sensor in bank 2, sensor 1
- Air/fuel sensor harness for bank 2, sensor 1 has a short or isn't properly connected
- Air/fuel sensor for bank 2, sensor 1 has a poor electrical connection
- ECM is faulty
Diagnosing the problem begins with a visual check to make sure the wiring harness is intact and properly connected. If wiring is intact and nothing has come loose, the next likely culprit is a faulty air/fuel sensor. It is not uncommon for air/fuel sensors to fail, they're only made to last about 50,000 miles in ideal conditions. They can also become damaged from heat and exposure to chemicals. These sensors are also often called "o2 sensors" or "oxygen sensors".
The more unlikely scenario is that the vehicle's ECM has gone bad, but if the code continues to light up the SES light after addressing these problems, a faulty ECM should be considered. Symptoms of this problem include a car that fails to start, automatic transmission shift problems, jerking and shaking in manual transmissions, and an explained loss in efficiency.
For a comprehensive list of trouble codes, check out this article on the Toyota Parts Center Blog.