P0158 — O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
Can drive — fix at your convenience.
What P0158 means
This code means the downstream oxygen sensor on bank 2 is reporting a continuously low voltage, which can point to a lean exhaust condition, a failing sensor, or a wiring fault. Because this sensor mainly tracks catalytic converter performance, the impact on how the car drives is usually small. It's commonly resolved by replacing the sensor or repairing its wiring, sometimes after fixing an exhaust leak.
Common symptoms
- Check engine light is on
- Usually normal driving with no obvious symptoms
- Possible slight drop in fuel economy
- Failed emissions test
- Faint exhaust leak noise in some cases
Common causes
- Failing downstream O2 sensor on bank 2
- Lean exhaust condition or air leak in the exhaust
- Short to ground in the sensor signal wire
- Corroded or damaged sensor connector
- Exhaust leak near the rear sensor
Typical repair cost
$150 – $350
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0158 code?
Usually yes. The rear sensor mainly monitors emissions, so the car typically drives fine. Get it diagnosed soon and before any emissions test, since the check engine light won't turn off on its own.
How much does it cost to fix a P0158 code?
Most repairs cost about $150 to $350. The downstream oxygen sensor and labor make up most of the bill, and a wiring or exhaust leak repair may be less.
Is a P0158 code serious?
It's generally low-severity. It rarely affects drivability, but it should still be fixed because it keeps the warning light on and can cause you to fail emissions testing.
What does low voltage mean in a P0158 code?
Oxygen sensors produce a small voltage that swings up and down as exhaust changes. A steady low reading suggests the sensor sees a lean exhaust or has an internal or wiring fault, which is why it gets flagged.