Error Code P0150 is defined as Oxygen Sensor Circuit Malfunction Bank 2 Sensor 1. This usually happens when the PCM (powertrain control module, or also called as ECM or engine control module in other makes) recognizes that the O2 (oxygen) sensor 1 bank 2 failed to meet the minimum or maximum voltage limit it was calibrated to, or the response of the voltage signal from the sensor takes longer than the specified time.

It’s a generic OBD-II code, meaning it appears to all vehicles equipped with OBD. Specifications and troubleshooting may differ from one make and model to another.


The Oxygen sensor produces voltage based on the exhaust’s oxygen content. This voltage will vary between 0.1 to 0.9V, with former indicating lean and the latter indicating rich. The sensor 1 is the first sensor at the downstream from the engine.

The PCM monitors the voltage continuously while in closed loop to find out how much fuel to inject. If it determines that the O2 sensor voltage is too low for too long (about 0.4V for more than 20 seconds (time and voltage may vary with make and model), then it trigger the Check Engine light and sets the Error Code P0150, referring to Bank 2.

Common Symptoms

Symptoms vary depending on the severity of the condition, or whether the problem is intermittent or not. The most obvious sign of course, is the illumination of the Check Engine light. If the problem is persistent, then it may show symptoms such as:

  • Rough running, misfiring or stumbling of the engine
  • Black smoke from the tail pipe
  • Engine dies
  • Poor fuel economy

Possible Causes

Error Code P0150 is usually caused by a bad O2 sensor. However, it can also be caused by other factors. For older oxygen sensors, there’s a big chance it’s what is causing the problem. But it could also be caused by:

  • Damaged or faulty O2 sensor
  • Water that leads to corrosion in the connector
  • Loose terminals in the connector
  • Burnt wiring on exhaust components
  • Open or short in the wiring caused by rubbing of engine components
  • Unmetered vacuum leak at the engine
  • Holes in the exhaust that allows unmetered O2 in to the exhaust system
  • Bad PCM (rare)

How to Check

To diagnose, scan the code and document the freeze frame data, and then clear the codes to verify. Then, monitor the oxygen sensor data for the voltage that will be switching back and forth between 0.2V and 1.2V. If the sensor is not within the specifications, then it should be replaced.

Then check the oxygen sensor wiring and the harness connections for any corrosion. Repair or replace any wiring or connectors that need fixing.

Check for leaks in the sensor and repair leaks that affects the sensor.

For a more thorough and accurate diagnosis, check the manufacturer’s specifications on pinpoints.

How to Fix

Repairs for this error code are pretty simple and straightforward. If the O2 sensor for bank 2 sensor is faulty, then it should be replaced.

Connectors and wirings to the O2 sensor for bank 2 sensor 1 should be fixed, if not replaced.

Repair leaks at the exhaust of the manifold for bank 2.

Error Code P0150 may cause the oxygen sensor to think it has too much oxygen in the exhaust, this will cause the PCM to enrich the mixture to compensate, which in the process results to excessive fuel consumption.

Also, the sensor may not be able to read correctly if there are exhaust leaks in front of it.

Unless the oxygen sensor is repaired and start working normally again, there’s a good chance the PCM will stay in open loop, extending the rich condition which may cause serious damage to engine components in the long haul.