P0151: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
Can you still drive? Yes, but the engine is running lean on Bank 2 which can increase exhaust temperatures. Repair within a couple of weeks to prevent catalytic converter damage.
What Does P0151 Mean?
Code P0151 means the upstream oxygen sensor on Bank 2 is reporting a consistently low voltage, typically below 0.2 volts. This indicates either a lean exhaust condition on Bank 2 or a sensor that has failed and is stuck reading lean. The ECU will attempt to compensate by enriching the fuel mixture, which can reduce efficiency.
Need to read your codes?
An OBD-II scanner lets you read and clear diagnostic trouble codes from your vehicle's computer. Most scanners work with any car made after 1996.
Browse OBD-II Scanners on AmazonCommon Causes
- Faulty O2 sensor stuck lean
- Vacuum leak on Bank 2 intake
- Exhaust leak before the sensor
- Low fuel pressure
Symptoms
- Check engine light on
- Lean running on Bank 2
- Reduced fuel economy
- Possible rough idle
- Failed emissions test
Diagnostic Steps
- 1Read and document freeze frame data
- 2Monitor Bank 2 Sensor 1 voltage to confirm stuck-low reading
- 3Check Bank 2 fuel trims for lean compensation
- 4Inspect for vacuum leaks on the Bank 2 side of the intake
- 5Check for exhaust leaks before the sensor
- 6Replace O2 sensor if the sensor is confirmed faulty
Recommended Parts & Tools
oxygen sensor
O2 sensor socket
Estimated Repair Cost
| Type | Estimated Cost |
|---|---|
| Total Repair Cost Range | $60 - $400 |
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Frequently Asked Questions
Can a vacuum leak cause P0151?
Yes, a vacuum leak on the Bank 2 side of the intake manifold can introduce unmetered air, creating an actual lean condition that causes the O2 sensor to read low voltage.
Should I replace just the Bank 2 sensor or both banks?
If only Bank 2 Sensor 1 has a code, you only need to replace that sensor. However, if the other upstream sensor is similarly aged, it may fail soon and some people choose to replace both preventatively.
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