P0157: O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)
Key takeaways
- P0157 means the downstream oxygen sensor on bank 2, the one after the catalytic converter, is reading lower voltage than it should for too long.
- It is safe to drive; the downstream sensor mainly checks the converter and does not control the fuel mixture on most cars.
- An exhaust leak ahead of the sensor, damaged wiring and a worn or oil-fouled sensor are the usual causes; a new sensor runs $150–$400.
- 15 manufacturer bulletins from 11 makes name P0157, pointing at software on GM trucks and SUVs and at valve cover oil leaks on Chrysler's 3.6L V6.
What P0157 means
The oxygen sensor behind your catalytic converter, on one side of the engine, is reporting a signal that stays too low.
Scanners call it O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2). Bank 2 is the side of a V engine without cylinder 1, so this code belongs to V6, V8 and flat engines. Sensor 2 is the downstream sensor, after the converter. A healthy downstream sensor reads a fairly steady voltage in the middle of its range. A low reading means it’s seeing lean exhaust (extra oxygen) or its signal wire is being pulled low. When the computer sees that for longer than it allows, it sets P0157.
Is it safe to drive?
Yes. On most cars the downstream sensor only watches the converter; it doesn’t decide how much fuel the engine gets, so the car drives normally. Book a repair in the next few weeks, since a lit check engine light fails emissions inspections in most states and hides any new code.
What changes the answer: the engine runs rough, the light flashes, or you also get lean codes like P0174 for bank 2. Then the problem is upstream and P0157 is only a symptom.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Exhaust leak ahead of the sensor | Ticking at a cold start, soot at a joint on the bank 2 side; smoke test of the exhaust | $150–$600 |
| Damaged wiring or connector | Melted or chafed wire near the exhaust, corroded plug; voltage drops when the harness is wiggled | $100–$250 |
| Worn or contaminated sensor | Circuit tests good but the sensor stays low and lazy on a scan tool | $150–$400 |
| Oil leaking onto the sensor | Oil on the sensor or exhaust from a valve cover leak above it | $150–$500 for the gasket, plus the sensor if it’s fouled |
| Engine software (some makes) | A bulletin matches your vehicle | $100–$200, often $0 under warranty |
| Engine actually running lean on bank 2 | Lean codes, high fuel trims on bank 2; the sensor is telling the truth | Start with a vacuum leak, $50–$400 |
What to check first
- Look for other codes. P0157 with P0161 (its heater) points to the sensor or its wiring. With P0137 (bank 1’s downstream sensor) at the same time, suspect software or a shared fuse before two sensors.
- Watch the sensor on a scan tool at warm idle and at 2,500 rpm. A flat low reading while the upstream sensors switch normally points to the sensor or wiring.
- Check for exhaust leaks between the engine and the sensor. Outside air pulled in at a leak reads as lean.
- Look for oil on the bank 2 exhaust and inspect the wiring along the pipe for heat or rodent damage.
- Ask about bulletins before buying a sensor. The pattern is software and oil. GM describes a software anomaly on 2014–2018 Silverado, Sierra, Tahoe, Suburban, Yukon and Escalade that sets P0132, P0137, P0152 and P0157 together, and an open emissions fuse on 2013–2015 Acadia, Enclave and Traverse. Chrysler traces the code on 2015–2017 3.6L V6 models (200, 300, Pacifica, Town and Country) to oil leaking from a valve cover gasket onto the sensor. Nissan and Infiniti have a 2015 Altima, Murano, Pathfinder and QX60 bulletin that may include an engine-computer reprogram.
- Clear it and drive. After a repair, clear the code and drive a few days to confirm it stays off.
What it costs
The cheap outcome is a wiring repair or a software update, $100–$250. The common outcome is a new downstream sensor, $150–$400. The expensive outcome is an exhaust leak repair, or a valve cover gasket plus a contaminated sensor, up to about $600. An hour of diagnosis, usually $100–$180, tells you whether the sensor is lying or telling the truth before you buy one.
Related codes
P0157 often shows with P0158 (the same sensor reading high) and P0161 (its heater). With P0430, check the converter and the sensor together, since the converter test on bank 2 relies on this sensor. For a wider look at O2 codes, see O2 sensor check engine light.
What owners report to NHTSA
1 complaints filed with NHTSA mention P0157, 1 of them since 2015, across 1 different models. The component owners most often filed it under: electronic stability control (esc).
Manufacturer service bulletins that name P0157
15 technical service bulletins and manufacturer communications filed with NHTSA mention P0157, from 11 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- CADILLAC ESCALADE (2015, 2016, 2017, 2018), bulletin 10160988: This Preliminary information communicatesCheck Engine Light on and vehicle runs rough. This condidtion will occur within the first 5 minutes after the vehicle is started.his condition may be caused by a software anomaly …
- CHEVROLET SILVERADO (2017, 2014, 2015, 2016), bulletin 10160988: This Preliminary information communicatesCheck Engine Light on and vehicle runs rough. This condidtion will occur within the first 5 minutes after the vehicle is started.his condition may be caused by a software anomaly …
- GMC SIERRA (2017, 2014, 2015, 2016), bulletin 10160988: This Preliminary information communicatesCheck Engine Light on and vehicle runs rough. This condidtion will occur within the first 5 minutes after the vehicle is started.his condition may be caused by a software anomaly …
- CHRYSLER 200 (2015, 2016, 2017), bulletin 10224882: Valve Cover and Gasket, Left and Right Pertains to vehicles equipped with a 3.6L V6 V.V.T. Engine only: Oil leaking from the valve cover onto the O2 sensor causing faults codes P0140, P2096, P0137, P0157. Need to verify …
- JAGUAR F-TYPE (2015, 2016), bulletin 10097084: "ISSUE: THE CUSTOMER MAY OBSERVE A MIL IN THE INSTRUMENT CLUSTER RELATING TO THE ENGINE SYSTEM (CHECK ENGINE LIGHT) AND ONE OR MORE CODES STORED IN THE PCM RELATING TO HEATED OXYGEN SENSOR (HO2S) IN THE EXHAUST SYSTEM. T…
- LAND ROVER RANGE ROVER (2016), bulletin 10105881: "ISSUE: THE CUSTOMER MAY OBSERVE A MIL IN THE INSTRUMENT CLUSTER RELATING TO THE ENGINE SYSTEM (CHECK ENGINE LIGHT) AND ONE OR MORE CODES STORED IN THE PCM RELATING TO HEATED OXYGEN SENSOR (HO2S) IN THE EXHAUST SYSTEM. T…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can I drive with a P0157 code?
Yes. The sensor after the converter doesn't run the engine on most cars, so it drives the same. Fix it before your next emissions test, because the light fails an inspection and hides any new code that sets.
Is P0157 a bad catalytic converter?
Usually not. A failing converter on bank 2 normally sets P0430. P0157 is about the sensor's voltage staying low, which points to the sensor, its wiring, or outside air leaking into the exhaust ahead of it.
Why do I have P0137 and P0157 together?
Both downstream sensors reading low at once points to something they share, such as engine software, a fuse, or oil or air getting into both sides of the exhaust. GM has a bulletin for exactly this on 2014–2018 full-size trucks and SUVs.
Will a new O2 sensor fix P0157?
Only if the sensor is the problem. Check for exhaust leaks, oil on the sensor and wiring damage first. If the code comes back soon after a new sensor, look for a leak or a bulletin.