P0158: O2 Sensor Circuit High Voltage (Bank 2, Sensor 2)

What does the P0158 error code mean?

The diagnostic trouble code, or DTC, P0158 indicates "O2 Sensor Circuit High Voltage (Bank 2, Sensor 2)." This code indicates that the downstream oxygen sensor on bank 2 is reporting a voltage that is higher than the expected range for an extended period. In this context, "downstream" indicates the sensor is located after the catalytic converter, not between the catalytic converter and the engine. This trouble code indicates that the sensor detects a rich air-fuel mixture or that the sensor or its circuit is malfunctioning. A rich air-fuel mixture means that there is too much gasoline and not enough air in the ratio, which can cause improper combustion.

Why is this issue important?

Oxygen sensors are critical pieces of equipment that monitor your car's emissions and ensure the engine operates as it should and at its most efficient. A high voltage reading from the downstream O2 sensor can affect your engine's ability to assess catalytic converter performance, which can lead to poor fuel economy or failed emissions tests. It can also be a contributing factor in more serious engine problems.

Can I safely drive my car with this error code?

Generally, you should avoid driving with a P0158 code. If absolutely necessary, the car can be driven without immediate danger to critical components so long as the engine is not running too rich (indicated by a gasoline smell in the car). It's best to replace the sensor as soon as possible.

Common symptoms of the P0158 error code

• Illuminated check engine light
• Poor fuel economy
• Fuel smell from within the car or at the exhaust
• Failing emissions tests
• A rough idle

How is the P0158 error code diagnosed?

• Scan the vehicle: Use a diagnostic tool to confirm the P0158 code
• Visual inspection: Visually inspect the O2 sensor and wiring for any sign of damage, a loose connection or corrosion.
• Sensor test: Monitor the sensor’s voltage using a scan tool or meter. Voltage consistently above 1.0 volt indicates a high signal condition.
• Fuel system inspection: Check the fuel system, lines, and injectors for leaks or poor fuel pressure, which can cause the engine to run rich.
• Exhaust check: Inspect for exhaust leaks before the sensor.

How is the P0158 error code repaired?

• Replace the applicable oxygen sensor if it is faulty or contaminated.
• Address the underlying causes of a rich air-fuel mixture, such as a leaking fuel injector or a failed fuel pressure regulator.
  

Related reading

Follow the link below to reach our diagnostic check engine trouble codes catalog:
On-board diagnostics (OBD-II) trouble code directory