Skip the auto shop - Our mechanics make house calls

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

Check Engine Light

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...
P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP)...


Related questions

Q: Po155cnf bank 2 sensor heater circuit P1620cnf Also code

The P0155 is the oxygen sensor located on the rear bank of cylinders and before the catalytic converter. Given your mileage, both oxygen sensors (pre-catalytic converter) should be replaced. The pre-cat sensors have the most affect on fuel mixture, saving...

Q: Where's vehicle speed sensor B ?

Hello, thanks for writing in about your Hyundai Azera. There isn't a certain answer for the sensor B. Here is the basic diagnostic route of trouble code P2159 to help you better understand the issue. If you'd like assistance with...

Q: Check engine sign on

Most Check Engine Lights are illuminated when an error code is triggered and stored in the ECM. Even if you've repaired what was broken or damaged, you still need to clear those codes in order for the light to go...