P0143 Code: O2 Sensor Circuit Low Voltage Bank 1 Sensor 3
🟠 Moderate severity · drivable
You can drive, but the engine may run rich to compensate and use more fuel until the sensor is replaced.
What P0143 means
The bank 1 sensor 3 oxygen sensor is sending a voltage that is too low. A healthy sensor switches between high and low voltage; a stuck-low reading means the sensor is weak or the circuit has a problem. This can make the computer think the exhaust is lean.
Symptoms
- Check engine light on
- Poor fuel economy
- Engine runs rich
- Rough idle
- Failed emissions test
Common causes
- most common: Faulty O2 sensor
- common: Wiring short to ground in the sensor circuit
- common: Exhaust leak
- less common: Contaminated sensor
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the O2 sensor | Yes | $80–200 |
| Repair the wiring short to ground | Yes | $20–80 |
| Fix the exhaust leak | Mechanic | $50–300 |
| Check for sensor contamination | Yes | $0–50 |
Frequently asked questions
Can I drive with P0143?
Yes, but the engine may run rich to compensate and use more fuel. Replace the sensor soon.
What does low voltage mean on an O2 sensor?
The sensor is stuck at a low voltage, which usually means it is worn out, grounded, or reading a lean exhaust.
Should I fix the exhaust leak first?
Yes, if there is a leak. A leak lets outside air in and gives false lean readings that can kill a new sensor.
Related codes
P0142
P0142 Code: O2 Sensor Circuit Bank 1 Sensor 3
P0144P0144 Code: O2 Sensor Circuit High Voltage Bank 1 Sensor 3
P0137P0137 Code: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.