P0155 OBD-II Trouble Code: 02 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)

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Cost of diagnosing the P0155 code

P0155 is a diagnostic trouble code (DTC) for "02 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $154.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $50.0 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate* Credit towards follow-up repair Earliest Availability
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Toyota $154.99 $50.0
BMW $164.99 $50.0

*Estimates may vary by market

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P0155 trouble code definition

O2 Oxygen Sensor Heater Circuit Malfunction (bank 2 sensor 1)

What the P0155 code means

When the P0155 code is present, it is an indication that the heater element of the oxygen sensor is taking longer than the normal to heat up. The power control module (PCM) will store the P0155 trouble code and the Check Engine Light will come on to alert the vehicle’s operator to the problem.

What causes the P0155 code?

  • The oxygen sensor (bank 2 sensor 1) not working properly
  • A broken or bare wire leading to the oxygen sensor
  • A fuse to the circuit for the oxygen sensor has blown
  • The engine coolant temperature sensor not working as it should
  • The power control module (PCM) is defective (much less likely)

What are the symptoms of the P0155 code?

  • The Check Engine Light is illuminated
  • The vehicle is running rough
  • The vehicle is consuming more fuel than usual
  • The vehicle is shutting off occasionally
  • There is a rotten egg smell coming from the exhaust
  • There is black smoke coming out of the exhaust

Some or all of these symptoms may be present with the P0155 trouble code.

How does a mechanic diagnose the P0155 code?

In most cases, the presence of this code indicates that the oxygen sensor needs to be replaced. Before doing so, the following steps should be taken:

  • Use an OBD-II scanner to collect the trouble codes that have been stored by the power control module (PCM).

  • Visually inspect the wiring that leads to the oxygen sensor for breaks in the wires or bare wires.

  • Use the OBD-II scanner to view live data in order to make sure the oxygen sensor is working properly.

  • If the coolant temperature sensor is not operating properly, the power control module (PCM) will store this code as well, so this should be inspected and tested as well.

  • In rare cases, the power control module (PCM) may be defective and this would require advanced diagnosis to make a determination as to whether this is the problem. This should be considered last, and only after every other possible attempt at repair has failed.

Common mistakes when diagnosing the P0155 code

  • Replacing the oxygen sensor before inspecting the other components

  • Not inspecting the wires leading to the oxygen sensor for breaks and/or bare wires before the oxygen sensor is replaced

How serious is the P0155 code?

The P0155 trouble code is considered to be a moderately serious code. The reason for this is that drivability problems and poor fuel consumption is possible when this trouble code is present.

What repairs can fix the P0155 code?

Additional comments for consideration regarding the P0155 code

The removal of the oxygen sensor can be difficult if you do not have an oxygen sensor set and propane tank. The oxygen sensor can be difficult to reach, depending on the vehicle. If the oxygen sensor has ceased in the exhaust, which is common, a heating element will be required to remove it.

Need help with a P0155 code?

YourMechanic offers certified mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

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Related questions

Getting multiple codes
Hello. When you get these codes together it is typically the result of a vacuum leak. If there is too much air entering the engine, your truck will have idling problems and this will cause issues with the oxygen sensor...
Po155cnf bank 2 sensor heater circuit P1620cnf Also code
The P0155 (https://www.yourmechanic.com/article/p0155-obd-ii-trouble-code-02-sensor-heater-circuit-malfunction-bank-2-sensor-1-by-jamahl-walker) is the oxygen sensor located on the rear bank of cylinders and before the catalytic converter. Given your mileage, both oxygen sensors (https://www.yourmechanic.com/services/oxygen-sensor-replacement) (pre-catalytic converter) should be replaced. The pre-cat sensors have the most affect on fuel...
Periodically vehicle runs rough at idle.
Hi there. Most of the codes that are coming on are for a misfire on cylinder number 3. Check the spark plug and wire on cylinder 3 and see if you are getting a good spark. Then check the fuel...

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