P1155 - FAULT CODE P1155 - OBD2

P1155 LEXUS, SCION, TOYOTA: AIR/FUEL RATIO SENSOR HEATER CIRCUIT MALFUNCTION BANK 2 SENSOR 1

The PCM (Powertrain Control Module) requires accurate air/fuel mixture readings to optimize fuel economy as well as emissions. If an inaccurate reading is sent to the control module, the amount of fuel required may not be enough or may exceed the required. That’s why many current model manufacturers use A/F (Air/Fuel) Sensors instead of conventional oxygen sensors. An A/F Sensor can read in a wider and narrower range of fuel mixtures.

The A/F Sensors have a heater that helps them get the temperature needed for good performance. A dedicated circuit controls the heater and using a pulse modulation, it regulates the temperature of the sensor, taking this action accurately. In Toyota cars, the PCM sends a reference signal corresponding to 3.0 v to the A/F Sensor. A detection circuit within the PCM monitors the changes in current flow and produces an output voltage signal proportional to the air/fuel mixture.

The setting of fault code P1155 OBDII for the manufacturers Lexus, Scion, and Toyota indicates that the heater circuit of the Air/Fuel Ratio Sensor 1 of bank 2 has experienced unstable operation.

• The Check Engine light is on.
• Difficult to start the engine during high temperatures
• The fuel loses performance.
• The engine power is reduced.
• Instabilities during idling.
• Poor acceleration.

The diagnostic code P1155 OBD2 is set because of the following reasons:

• Sensor A/F 1 circuit cables or connectors may be defective.
• Air/Fuel Ratio Sensor 1 control circuit connections may be shorted or have an open circuit causing the malfunction.
• The A/F Sensor may be defective.

The steps to solve the DTC code P1155 OBDII are the following:

• As a first step, we recommend you consult the TSB (Technical Service Bulletins).
• Check for air leaks, especially near the installation of the Air/Fuel Ratio Sensor Also, check the electrical circuit components of this sensor for deficiencies due to burns, corrosion or other conditions.
• Perform voltage tests on the A/F Sensor circuit and verify that these are within the parameters set by the manufacturer. If inconsistencies are found, make the proper corrections.
• Check the integrity of the Air/Fuel Ratio Sensor If you find that the sensor is damaged, replace it.