OBD codes / P0157
P0157
ModerateO2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)
P0157 is low-urgency for drivability — the downstream sensor mostly monitors the catalytic converter rather than controlling the engine. You can drive normally in the short term, but fix it before an emissions test, and rule out a real lean condition (P0174) so you are not masking a bigger problem.
What this code means
Bank 2, Sensor 2 is the oxygen sensor sitting after the catalytic converter on the side of the engine opposite cylinder 1 — so this code only applies to V6, V8, and flat engines, not inline-4s. Its main job is watching how well the catalytic converter is working, not controlling the fuel mixture, which is why this code rarely changes how the car drives. P0157 sets when that sensor's voltage stays pinned low, as if the exhaust were extremely lean, for longer than the computer allows. The usual suspects are a failing sensor, a signal wire shorted to ground, or an exhaust leak near the sensor pulling in outside air. A genuine lean condition on that bank can also do it — if P0174 is present too, chase the lean problem first.
Symptoms you might notice
- Check-engine light with little or no change in how the car drives
- Possible slight dip in fuel economy
- Failed emissions test while the light is on
- Occasionally appears alongside lean codes like P0174
What it costs to fix
Typical range: $100–$450 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| O2 sensor (Bank 2, Sensor 2) | $30–$200 | ~0.3–1 hrs |
| Wiring or connector repair | $5–$60 | ~0.5–1.5 hrs |
| Exhaust leak repair (gasket or flange) | $15–$100 | ~0.5–1.5 hrs |
Downstream sensors are usually cheaper than upstream ones and often easy to reach from under the car. The wildcard is a seized sensor in a rusty exhaust — on high-mileage or rust-belt vehicles, extracting a stuck sensor can add real labor time.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0157 for my exact vehicle →
Frequently asked
Can I keep driving with P0157?
Yes, in most cases. The bank 2 downstream sensor is mainly a catalytic converter monitor, so the engine keeps running normally. The main consequences are a lit check-engine light, a failed emissions test, and the fact that the computer can no longer watch that converter's health.
Does P0157 mean my catalytic converter is bad?
No — it points at the sensor circuit, not the converter itself. That said, this sensor is the one the computer uses to judge that converter, so fixing P0157 matters: until it works, a converter problem on that side (which would set P0430) could go undetected.
Why does my car have a Bank 2 code at all?
Bank 2 is the cylinder bank that does not contain cylinder 1, so it only exists on V-type and flat engines. If you drive an inline-4, this code should not appear; on a V6 or V8, Bank 2 is simply the other side of the engine from Bank 1.
Is P0157 usually the sensor or the wiring?
The sensor itself is the most common fix, but a low-voltage code specifically can also be a signal wire grounding out, so it is worth a quick wiring inspection first. Downstream sensor harnesses run along the underbody where they can chafe, melt against the exhaust, or corrode.
Seeing P0157 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0157 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0157 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.