P0157: O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)

What does the P0157 error code mean?

The P0157 diagnostic trouble code stands for "Oxygen Sensor Circuit Low Voltage (Bank 2, Sensor 2)." This code indicates that the powertrain control module has detected a low voltage signal from the downstream oxygen sensor on Bank 2. The downstream oxygen sensor monitors the efficiency of the catalytic converter by measuring the oxygen levels in the exhaust gases after they pass through the converter.

Why is P0157 important to address?

A malfunctioning downstream oxygen sensor can cause improper monitoring of the catalytic converter. It is important for the oxygen sensor to function properly so it can detect potential issues with the catalytic converter.

Can I safely drive my car with this error code?

While the vehicle may remain operational with the P0157 code, driving for extended periods is not advisable. If the sensor is not working properly and there is an issue with the catalytic converter, this can lead to excessive emissions and potential damage to the converter or other components. Addressing the issue promptly will help avoid further complications.

Common symptoms of the P0157 error code

• Illuminated check engine light
• Decreased fuel efficiency
• Failed emissions test
• Potential fuel odor from the exhaust
• Slight reduction in engine performance (in rare cases)

How is the P0157 error code diagnosed?

Diagnosing the P0157 code involves the following steps:

• Scan for codes: Use an OBD-II scanner to confirm the P0157 code and identify any related codes.
• Inspect the oxygen sensor and wiring: Check the downstream oxygen sensor on Bank 2 for damage, corrosion or loose connections.
• Test the sensor voltage: Use a multimeter to measure the voltage output from the sensor and compare it to the manufacturer’s specifications.
• Check the catalytic converter: Inspect the converter for blockages, damage, or inefficiency that could affect the oxygen sensor readings.
• Evaluate the powertrain control module: If no issues are found with the sensor or converter, test the powertrain control module for potential faults in signal processing.

How is the P0157 error code repaired?

Repairs for the P0157 code typically include:

• Replacing the faulty downstream oxygen sensor on Bank 2.
• Repairing or replacing damaged wiring or connectors in the sensor circuit.
• Cleaning or replacing the catalytic converter if it is clogged or damaged.
• Updating or reprogramming the powertrain control module if required.
• Clearing the code with an OBD-II scanner and performing a test drive to ensure the issue is resolved.

Related reading

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