P2273
Sensor Signal Biased/Stuck Rich Bank 2 Sensor 2P2273 is a generic OBD-II powertrain diagnostic trouble code: Sensor Signal Biased/Stuck Rich Bank 2 Sensor 2. It is logged by the engine control unit when the scr/adblue monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P2273 means
P2273 is logged when the ECM detects that the downstream oxygen sensor on Bank 2 (Sensor 2, after the catalytic converter) is stuck rich — that is, the sensor voltage is fixed at a high level, typically above 0.7–0.9 V, and refuses to swing lean when it should. In normal operation this sensor monitors catalyst oxygen-storage capacity; a flat high-voltage signal means the exhaust exiting the catalyst is consistently low in oxygen, suggesting the catalyst is saturated, ageing, or contaminated.
The most frequent real-world culprits are a deteriorating catalytic converter that can no longer burn off hydrocarbons, or a degraded sensor whose reference cell has drifted to produce a permanently rich bias. Engine oil or coolant entering the combustion chamber and passing through the exhaust will coat and poison the sensor element, causing the same locked-high output. A stuck-open EVAP purge valve that continuously bleeds raw fuel vapour into the intake is another common but easily overlooked cause, as the resulting rich exhaust is seen first by the downstream sensor.
P2273 rarely produces obvious driveability symptoms on its own because the affected sensor primarily monitors catalyst health rather than controlling the air-fuel ratio. Nevertheless, persistent rich exhaust accelerates catalyst overheating and failure, and a genuine rich running condition will shorten injector and engine life if left unresolved. Fuel trim analysis, an EVAP purge valve functional test, and a compression/leakdown test to rule out oil or coolant consumption should form the diagnostic foundation.
Common causes
Most-frequently reported root causes when P2273 is logged.
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1
Degraded catalytic converter saturated with hydrocarbons and no longer able to store or consume oxygen.
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2
Failed downstream O2 sensor with a drifted or poisoned electrochemical cell generating a persistently high voltage output.
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3
Engine oil entering the exhaust (due to worn valve seals or rings) contaminating and poisoning the O2 sensor.
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4
Coolant leak into a combustion chamber depositing silicates on the sensor element.
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5
Stuck-open EVAP purge valve bleeding excess fuel vapour into the intake, causing a genuine rich exhaust condition.
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6
High fuel pressure, stuck-open injector, or MAF sensor over-reading causing sustained over-fuelling on Bank 2.
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7
Corroded or damaged wiring dragging the sensor signal line toward the supply voltage reference.
Symptoms drivers notice
How to diagnose P2273
A typical diagnostic flow when this code is present.
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1
Connect a scan tool and record all stored codes; pay particular attention to companion codes such as P0430 (catalyst efficiency), P0172 (system rich Bank 2), or any EVAP codes.
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2
Monitor Bank 2 Sensor 2 live voltage with the engine fully warm; a reading persistently above 0.8 V with no lean swings confirms the stuck-rich fault.
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3
Check Bank 2 short-term and long-term fuel trims; positive trims indicate the ECM is trying to lean out a genuine rich condition, pointing away from a failed sensor.
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4
Perform a functional test on the EVAP purge valve — command it closed via the scan tool and observe whether fuel trims and O2 voltage normalise.
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5
Inspect the engine for oil consumption (blue smoke, low oil level) and for coolant loss; both contaminate the downstream sensor element.
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6
With the sensor unplugged, measure the signal circuit resistance and voltage; a high-resistance short to the 5 V reference line mimics a rich signal and warrants harness repair before sensor replacement.
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7
Replace the Bank 2 Sensor 2 oxygen sensor if the catalytic converter tests within spec and no rich fuel condition or sensor contamination source has been identified.
Related powertrain codes
- B0001 — PCM Discrete Input Speed Signal Error
- B0004 — PCM Discrete Input Speed Signal Not Present
- C0359 — Four Wheel Drive Low Range (4LO) Discrete Output Circuit
- C0362 — 4LO Discrete Output Circuit High
- P2000 — NOx Adsorber Efficiency Below Threshold Bank 1
- P2001 — NOx Adsorber Efficiency Below Threshold Bank 2
Frequently asked questions
Does P2273 mean my catalytic converter needs replacing?
Not necessarily, but it is a strong indicator of a degraded catalyst on Bank 2. If the code appears together with P0430 (catalyst efficiency low) and fuel trims are normal, the converter is the likely cause. If fuel trims are significantly positive, address the rich running condition first, as a good catalyst can be destroyed by sustained over-fuelling.
Can engine oil burning set P2273?
Yes. Oil vapour passing through the exhaust coats the O2 sensor's zirconia element with combustion by-products, altering its reference voltage and biasing the output high. Blue smoke from the exhaust and falling oil level are clues to check before replacing the sensor.
Is P2273 the same as P0172 (system rich Bank 2)?
No. P0172 means the upstream, closed-loop sensor has detected a rich mixture and the ECM has adjusted fuelling — it reflects actual over-fuelling. P2273 is specific to the downstream monitor sensor behaving as though it is stuck high, which may or may not correlate with a genuine rich condition.
How urgent is it to fix P2273?
The vehicle can typically be driven short-term without immediate safety risk. However, if a genuine rich condition or catalyst problem underlies the code, prolonged operation will accelerate catalyst failure and increase emissions. Diagnosis within a few hundred miles is advisable.
Disabling P2273 in software
RaceTune can permanently disable P2273 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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