OBD-II trouble code
P2276: O2 Sensor Signal Biased/Stuck Lean (Bank 2, Sensor 3)
The rearmost oxygen sensor on Bank 2 is stuck low. On a two-bank engine the opposite bank's matching sensor is a free reference, and comparing them is the fastest way to tell a local fault from an engine-wide one.
Quick facts
- System
- Powertrain
- Category
- Oxygen Sensor
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $480
- DIY difficulty
- Intermediate DIY
Browse every code in P2200–P229F, or start from the full code library.
What does P2276 mean?
Bank 2 is the cylinder bank that does not contain cylinder 1, so this code only appears on V-type, flat or W-configuration engines. Sensor 3 is the rearmost sensor on that bank, sitting behind the second catalyst in the series. P2276 means its signal is parked toward the lean end and is no longer moving the way the module expects.
Having two banks is the practical advantage this code offers over its Bank 1 equivalent. Both banks are fed the same fuel from the same rail, breathe the same air through the same intake and are commanded by the same strategy. So when Bank 2 Sensor 3 reads flat and low while Bank 1 Sensor 3 looks normal at the same instant, the problem is physically on the Bank 2 side of the exhaust — that one sensor, its wiring or the pipe around it — and everything upstream is exonerated without a meter. If both rear sensors read lean together, the fault is shared, and the search moves to the fuel supply, the intake or a failing rear catalyst common to both.
Before relying on that comparison, check the exhaust layout, because it is the trap specific to this address. Many V engines run dual pipes only as far as a Y-junction and then use a single underfloor converter and a single post-converter sensor. When the two banks have merged before the rearmost sensor, that sensor is reading a blended stream and a bank-specific conclusion from it is not available. Look under the vehicle before reasoning about banks.
Routing is the other Bank 2 particularity. On transverse V6 installations the second bank is the one against the firewall, and its rear sensor harness usually runs back along the transmission tunnel, clipped alongside heat shields, before it reaches a connector. It is a longer, hotter run than the Bank 1 side of the same vehicle, and that is where chafe and heat damage on this circuit are normally found.
Common causes
- Exhaust leak on the Bank 2 side ahead of the rear sensor drawing in outside air
- Aged or slow Bank 2 rear sensor at the end of its service life
- Harness chafe or heat damage along the transmission tunnel where the Bank 2 rear circuit is routed
- Corroded or waterlogged connector on the Bank 2 rear sensor
- Failed sensor heater leaving the element cold on short trips
- Genuine lean post-catalyst condition affecting Bank 2 specifically
- Diagnosis attempted on a merged exhaust where the rearmost sensor is not bank-specific at all
Symptoms
- Check engine light with no driveability change
- Bank 2 Sensor 3 live data low and flat while Bank 1 Sensor 3 behaves normally
- Catalyst readiness monitor stuck incomplete
- Failed emissions inspection on readiness
- Possible companion Bank 2 catalyst code such as P0430
- Occasionally an exhaust leak audible from the Bank 2 side when cold
Diagnostic steps
- 1.Look at the exhaust layout under the vehicle and confirm the two banks are still separate where the rearmost sensors sit. If they merge first, bank-specific reasoning does not apply.
- 2.Graph Bank 1 Sensor 3 and Bank 2 Sensor 3 on the same screen and compare them at the same moment. One flat and one normal means a local Bank 2 fault; both flat means look upstream.
- 3.Read all codes. A companion P0430 points toward the Bank 2 converters rather than the sensor alone.
- 4.Inspect the Bank 2 exhaust from the rear converter forward with the engine cold and running — leaks close up as the system heats and expands.
- 5.Follow the Bank 2 rear harness along the transmission tunnel, checking every clip and heat shield contact point for chafe, melt or a conductor showing through.
- 6.Open and inspect the connector for water, corrosion and spread terminals.
- 7.Check heater circuit operation if the signal is slow to become active after a cold start.
- 8.Replace the Bank 2 rear sensor last, after the exhaust and harness on that side have been proven sound.
Repair cost
$150 – $480
Bank 2 rear sensor replacement typically runs $150 to $480 fitted. The part is usually $50 to $180 and is the same unit as the Bank 1 rear sensor on most vehicles, but the Bank 2 harness run is longer and less accessible, so a wiring repair on this side costs more than the equivalent Bank 1 job. Exhaust leak repair ahead of the sensor adds roughly $100 to $400.
Estimate your repair
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Open the Repair Cost Estimator with oxygen sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.