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?
- Fix broken wires or bare wires
- Replace the coolant temperature sensor
- Replace the oxygen sensor
- Replace the power control module (PCM), in the rare case that it is necessary
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?
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This article originally appeared on YourMechanic.com as P0155 OBD-II Trouble Code: 02 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1) and was authored by Jamahl Walker.