General Fault Code for Air/Fuel Sensor Heater Circuit Response - Bank 1, Sensor 1
OBD-II code P1135 represents a general fault in the air/fuel sensor heater circuit for bank 1, sensor 1.
The air/fuel ratio sensor needs to reach a certain operating temperature, a minimum of 1200 degrees Fahrenheit, to create accurate voltage signals. The sooner the air/fuel ratio sensor gets to that minimum temperature, the quicker the sensor will begin to send accurate signals to the ECM, or engine control module.
To reach the required operating temperature, a heater element is built into the air/fuel ratio sensor. The air/fuel ratio sensor heater element is controlled by the ECM based on signals coming from engine coolant temp and engine load. Voltage signals received through the heater element circuit are monitored by the ECM, which determines the state of the circuit by comparing voltage with factory specifications.
When there is a problem detecting this signal, that's where the code P1135 comes from. The occurrence of this code will cause a check engine light or SES light to illuminate on your dash.
What Causes Toyota Code P1135?
The majority of the time, the P1135 code initiates from these causes:
- Faulty air/fuel ratio sensor in bank 1, sensor 1
- Air/fuel sensor harness for bank 1, sensor 1 has a short or isn't properly connected
- Air/fuel sensor for bank 1, sensor 1 has a poor electrical connection
- ECM is faulty
The first step in diagnosis is visually checking the wiring for the harness to make sure no wires are damaged. Next, check the connections to make sure nothing has pulled loose. From there, replacement of the sensor is your best bet; a bad sensor is almost always the cause of this code and is a very common occurrence. The air/fuel sensors are made to be replaced; their position on your Toyota makes them vulnerable to heat damage; they may also be damaged from coming in contact with certain things like antifreeze/coolant. Most are made to only last 50,000 miles without damage from outside factors. These sensors are also commonly called "oxygen sensors" or "o2 sensors".
The most uncommon problem associated with this code is a faulty ECM; however, if you've addressed the other causes and the light remains on, it is possible that your EMC is problematic. Other symptoms of a bad ECM include a car that won't start, poor performance, an unexplained drop in efficiency, problems in shifting with an automatic transmission, and jerking and stalling with manual transmission.
For a comprehensive list of trouble codes, check out this article on the Toyota Parts Center Blog.