P0157
O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
The engine computer is seeing a very low signal from the rear oxygen sensor on bank 2. This usually means the sensor, its wiring, or the exhaust leak near it has a problem. It can also be caused by a fuel mixture issue or a bad heater circuit in the sensor.
- SEV
- 3/5
- DRIVE
- CAUTION
- DIY
- $20–$120
- SHOP
- $120–$450
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty Bank 2 Sensor 2 oxygen sensor
- Damaged, corroded, or loose wiring or connector for the rear O2 sensor
- Exhaust leak near the sensor or before it
Typical repair cost
DIY usually runs $20–$120. Typical shop repair lands around $120–$450, depending on the root cause.
01 / Definition
P0157 means the powertrain control module has detected a low-voltage condition from the Bank 2 Sensor 2 oxygen sensor circuit. Bank 2 Sensor 2 is the rear O2 sensor on the bank opposite cylinder 1, usually located after the catalytic converter. The code points to an electrical or exhaust-related fault more often than a catalytic converter failure itself.
02 / Drive status
With caution. The vehicle may still drive, but the problem can affect emissions, fuel economy, and how the engine computer monitors the catalytic converter. If the engine runs poorly, stalls, or other warning lights appear, diagnose it promptly.
03 / Symptoms
- Check engine light on
- Possible reduced fuel economy
- Failed emissions test
- Stored or pending oxygen sensor codes
- Occasional rough running if another engine problem is present
- No obvious drivability symptoms in many cases
04 / Causes
| 1 | Faulty Bank 2 Sensor 2 oxygen sensor | high |
|---|---|---|
| 2 | Damaged, corroded, or loose wiring or connector for the rear O2 sensor | high |
| 3 | Exhaust leak near the sensor or before it | medium |
| 4 | Failed oxygen sensor heater circuit or power supply issue | medium |
| 5 | Rich or lean engine condition affecting sensor readings | medium |
| 6 | Blown fuse, bad relay, or PCM driver issue | low |
05 / Diagnostic sequence
- 01Scan for all stored and pending codes and freeze-frame data.
- 02Inspect Bank 2 Sensor 2 wiring, connector, and harness for heat damage, corrosion, loose pins, or rubbing.
- 03Check for exhaust leaks near the rear oxygen sensor and along the exhaust before it.
- 04Verify the sensor heater circuit has power and ground according to the wiring diagram.
- 05Review live data for Bank 2 Sensor 2 and compare it with Bank 1 Sensor 2 if equipped.
- 06Test the sensor signal and wiring with a multimeter or scan tool if available.
- 07If wiring and exhaust are good, replace the sensor and clear codes.
- 08If the code returns, inspect PCM power, grounds, and circuit integrity more deeply.
06 / Repairs
| 1 | Repair damaged wiring, terminals, or connector at Bank 2 Sensor 2 | $20–$150 |
|---|---|---|
| 2 | Fix any exhaust leak near the rear oxygen sensor | $50–$250 |
| 3 | Replace Bank 2 Sensor 2 oxygen sensor | $40–$180 |
| 4 | Repair heater circuit power, fuse, or relay issue | $20–$200 |
| 5 | Perform further diagnosis for fuel mixture or PCM faults if the code persists | $0–$300 |
07 / Related codes
08 / FAQ
Is P0157 the same as a bad catalytic converter?
Not usually. P0157 points to the rear oxygen sensor circuit on bank 2, not directly to the catalytic converter.
Can a bad oxygen sensor wiring cause P0157?
Yes. Wiring damage, corrosion, or a loose connector is a common cause of this code.
Will replacing the sensor always fix P0157?
No. If the wiring, connector, heater circuit, or exhaust has a problem, the code can come back after sensor replacement.
Can I keep driving with P0157?
Usually yes for short-term use, but it should be diagnosed soon because it can affect emissions and fuel economy.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.