P0157: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
Can you still drive? Yes, safe to drive. This is a monitoring sensor with no direct impact on engine control. Address it when convenient or before emissions testing.
What Does P0157 Mean?
Code P0157 means the downstream oxygen sensor on Bank 2 is consistently reading a low voltage, below 0.2 volts. This indicates the sensor is detecting a lean exhaust condition after the catalytic converter, or more commonly, the sensor itself has failed and is stuck reading low. This affects the ECU's ability to monitor converter 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
- Failed downstream O2 sensor
- Exhaust leak after the catalytic converter
- High-resistance connection in sensor wiring
- Lean exhaust condition reaching downstream sensor
Symptoms
- Check engine light on
- Failed emissions test
- Marginally reduced fuel economy
- No significant drivability symptoms
Diagnostic Steps
- 1Read and document freeze frame data
- 2Monitor Bank 2 Sensor 2 voltage to confirm stuck-low
- 3Check for exhaust leaks near the downstream sensor
- 4Inspect wiring for high resistance or damage
- 5Compare Bank 2 Sensor 2 readings to Bank 1 Sensor 2
- 6Replace sensor if confirmed faulty
Recommended Parts & Tools
oxygen sensor
O2 sensor socket
penetrating oil
Estimated Repair Cost
| Type | Estimated Cost |
|---|---|
| Total Repair Cost Range | $60 - $350 |
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Chat with AI About P0157Commonly Affected Vehicles
Related Recalls
1 Active Recall — 2026 Ford Expedition
The following NHTSA safety recalls have been issued for this vehicle. Contact your dealer to check if your vehicle is affected.
ELECTRICAL SYSTEM: INTEGRATED TRAILER BRAKE CONTROL
Ford Motor Company (Ford) is recalling certain 2021-2026 F-150, 2022-2026 F-250 SD, F-350 SD, F-450 SD, F-550 SD, Maverick, 2024-2026 Ranger, 2023-2026 F-600 SD, 2022-2027 Lincoln Navigator, Expedition, and 2026 E-Transit vehicles. When towing a trailer, the integrated trailer module (ITRM) may lose communication with the vehicle, possibly causing a loss of brake and turn signal lights, or a loss of brake function. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 108, " Lamps, Reflective Devices, and Associated Equipment."
Remedy: The integrated trailer module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters are expected to be mailed March 17, 2026. Owners may contact Ford customer service at 1-866-436-7332. Ford's number for this recall is 26C10. Vehicle Identification Numbers (VINs) involved in this recall will be searchable on NHTSA.gov beginning March 17, 2026.
Data provided by the National Highway Traffic Safety Administration (NHTSA).
Frequently Asked Questions
Why does only the Bank 2 downstream sensor fail?
Downstream sensors on Bank 2 are often more exposed to road spray, debris, and temperature cycling depending on the vehicle layout. They can fail independently of Bank 1 sensors.
Can an exhaust leak cause P0157?
Yes, an exhaust leak near the downstream sensor allows fresh air to reach the sensor, making it read lean (low voltage) even if the exhaust is actually at normal levels.
Community Fix Reports
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