OBD-II trouble code
P2273: O2 Sensor Signal Stuck Rich (Bank 2, Sensor 2)
The post-catalyst sensor on Bank 2 is stuck high. Because this code only exists on two-bank engines, you have something no single-bank vehicle offers — an identical sensor on the other side to check the reading against.
Quick facts
- System
- Powertrain
- Category
- Oxygen Sensor
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $500
- DIY difficulty
- Intermediate DIY
What does P2273 mean?
A code naming Bank 2 tells you something about the engine before it tells you anything about the fault. Only V, flat and W layouts have a second cylinder bank, so P2273 cannot occur on an inline engine. That single deduction is worth more than it looks, because it guarantees the existence of a piece of test equipment already bolted to the vehicle: an identical post-catalyst sensor, in the same position, of the same age and the same part number, sitting on Bank 1.
Use it. Park the vehicle overnight so both sensors cool to ambient, then compare the two readings at key-on and again through a warm-up. Two sensors looking at the same air, in the same conditions, on the same vehicle, have no legitimate reason to disagree. If Bank 2 sits high while Bank 1 behaves normally, the sensor has been identified without a specification lookup, a wiring diagram or a single meter lead. That comparison is not available on a four-cylinder, which is why this page is worth reading differently from its Bank 1 counterpart.
The inverse result is the more important one, and it saves real money. If both banks read stuck rich, no sensor is at fault — two sensors do not fail identically at the same moment. Something both banks share is making the exhaust genuinely rich, and everything upstream of the cylinder heads is shared: fuel pressure, the pump, the regulator, the filter, evaporative purge, intake air measurement. Replacing sensors in that situation fixes nothing and the codes return within a drive cycle or two.
If the comparison does confirm one bank only, the cause list for a genuine single-bank rich condition is short and specific, because a shared component cannot produce a one-sided result. What remains are faults belonging to that bank alone: a leaking injector on those cylinders, that bank's camshaft timing, that bank's intake manifold gasket, or a contaminated sensor. Narrowing a rich condition to one bank is diagnostic progress that a single-bank engine simply cannot offer.
One practical note on quoting. A two-bank engine of this type usually carries four oxygen sensors and two catalytic converters. "The oxygen sensors are bad" is therefore a four-part sentence unless someone specifies which one, and the two rear positions are rarely equal in labour even though they share a part number. Ask for the quote itemised by position.
Common causes
- Contaminated or aged post-catalyst sensor on Bank 2 that can no longer switch
- A genuinely rich condition confined to Bank 2 — a leaking injector on those cylinders, that bank's cam timing, or that bank's intake gasket
- A shared fuelling fault making both banks rich, in which case Bank 1 will show the same behaviour and no sensor needs replacing
- Oil or coolant entering the exhaust on that bank and coating the element
- Damaged or corroded connector and wiring on the Bank 2 sensor lead
- Sensor heater fault leaving the element below operating temperature and unable to respond
Symptoms
- Check engine light on
- Bank 2 post-catalyst sensor pinned high in live data while Bank 1 behaves normally
- Catalyst efficiency code for Bank 2 sometimes stored alongside it
- Emissions inspection failed
- Rarely any driveability symptom unless the exhaust is genuinely rich on that bank
- Fuel trims skewed on Bank 2 only, if the rich condition is real
Diagnostic steps
- 1.Confirm the engine has two banks and identify which side is Bank 2 in service data. Cylinder numbering is manufacturer-specific and guessing costs a healthy sensor.
- 2.Graph both post-catalyst sensors on the same screen. This side-by-side comparison is the fastest and most decisive test available on this code and it costs nothing.
- 3.Let the vehicle sit overnight and compare both readings from a genuine cold start. Two sensors seeing the same ambient air must agree; the one that does not is the liar.
- 4.If BOTH banks read stuck rich, stop looking at sensors. Check fuel pressure, the regulator, evaporative purge and intake air measurement — a one-sided fault cannot come from a shared component, and a two-sided one cannot come from a single sensor.
- 5.If only Bank 2 is affected, compare fuel trims bank to bank, then investigate causes belonging to that bank alone: injector leakage on those cylinders, camshaft timing, and intake manifold sealing.
- 6.Remove the sensor and inspect the tip for contamination before fitting a replacement, and check the connector and heater circuit on that bank's lead.
- 7.If a Bank 2 catalyst efficiency code is stored too, repair this sensor first and let the monitor re-run before forming any view about that converter.
Repair cost
$150 – $500
Post-catalyst sensor replacement is roughly $150 to $500 fitted. The part is the same as the Bank 1 sensor; the spread is labour, because the two rear positions on a V engine are seldom equally accessible. If the comparison shows both banks rich, the repair is a fuelling fault instead — a leaking injector at $200 to $600, or a fuel pressure regulator at $150 to $450 — and no sensor is needed at all.
Estimate your repair
Run the numbers for your vehicle
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.