P0155 Code: Oxygen Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)

p0155 code written in white with an orange and blue background color

A P0155 is a generic code for a failed oxygen sensor heater circuit. 

What You'll Read About

What is the P0155 code?

The P0155 code means that the oxygen sensor heater circuit is not working. The oxygen sensor heater is used to warm up the sensor before it’s used, preventing it from being damaged by cold weather.

Symptoms of a P0155 Code

  • Check engine light: The check engine light will illuminate on the dashboard, indicating a problem with the engine or emissions system.
  • Poor fuel economy: A faulty oxygen sensor can cause the engine to run rich or lean, which can result in decreased fuel efficiency.
  • Engine runs rough: An oxygen sensor that is not working correctly can cause the engine to run rough, idle poorly, or hesitate during acceleration.
  • Increased emissions: A malfunctioning oxygen sensor can cause the vehicle to produce higher emissions, which can result in a failed emissions test.
  • Loss of power: A bad oxygen sensor can cause the engine to lose power, which can be noticeable during acceleration.

Causes of a P0155 Code

The oxygen sensor heater circuit is open when there is a break in the circuit between the PCM and the oxygen sensor. If this happens, it can cause an Air/Fuel ratio to be incorrect.

The oxygen sensor heater circuit is shorted when current is flowing through all of the wires in a single direction instead of alternating positive and negative voltages as it should be doing. This will also cause an Air/Fuel ratio to be incorrect.

The oxygen sensor heater circuit could be grounded if one of its components touches ground at any point along its path from PCM to O2S or vice versa (or both). This would result in an incorrect Air/Fuel ratio reading as well due to no voltage reaching either end of your car’s wiring system!

Causes of a P0155 Code

The oxygen sensor heater circuit is open when there is a break in the circuit between the PCM and the oxygen sensor. If this happens, it can cause an Air/Fuel ratio to be incorrect.

The oxygen sensor heater circuit is shorted when current is flowing through all of the wires in a single direction instead of alternating positive and negative voltages as it should be doing. This will also cause an Air/Fuel ratio to be incorrect.

The oxygen sensor heater circuit could be grounded if one of its components touches ground at any point along its path from PCM to O2S or vice versa (or both). This would result in an incorrect Air/Fuel ratio reading as well due to no voltage reaching either end of your car’s wiring system!

Diagnosing a P0155 Code

  • Check the oxygen sensor.
  • Check for loose or broken wiring in the harness between this sensor and its corresponding ECU relay.
  • Inspect fuel system components, including injectors, fuel pump and pressure regulator (if equipped) for leaks or other damage that could affect their operation

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