P0151 Code: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
🟠 Moderate severity · drivable
Drivable, but the engine may run lean and rough. Fix it soon for proper fuel control.
What P0151 means
The bank 2 upstream oxygen sensor is reporting very low voltage, which the computer reads as a lean mixture on bank 2.
Symptoms
- Check engine light is on
- Rough running or hesitation
- Poor fuel economy
Common causes
- most common: Vacuum leak causing a genuine lean condition
- common: Faulty upstream oxygen sensor (bank 2)
- common: Exhaust leak before the sensor
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Find and repair vacuum leaks | Yes | $10–100 |
| Replace the bank 2 upstream oxygen sensor | Yes | $60–200 |
| Repair an exhaust leak near the sensor | Mechanic | $50–200 |
Frequently asked questions
Can I drive with a P0151 code?
Yes, but the engine may run lean and rough. Fix it soon.
What is the most common cause of P0151?
A vacuum leak causing a genuine lean condition, or a faulty oxygen sensor.
How much does it cost to fix a P0151?
$10–$100 for a vacuum leak, or $60–$200 for a new sensor.
Related codes
P0150
P0150 Code: O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)
P0152P0152 Code: O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
P0174P0174 Code: System Too Lean (Bank 2)
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.