How is P2273 different from P2271?

They're the same fault on opposite banks. P2271 is the downstream sensor on Bank 1 stuck rich; P2273 is the downstream sensor on Bank 2 stuck rich. Both are emissions/catalyst-monitoring codes that rarely affect driveability.

Which side is Bank 2?

Bank 2 is the cylinder head that does not contain cylinder 1 on a V6, V8, or similar engine. Inline engines have only Bank 1 and never set P2273. Confirm which physical side is Bank 2 for your engine before diagnosing.

Is P2273 safe to ignore?

It won't strand you, but it will fail an emissions inspection and can accompany a Bank 2 catalyst problem. Diagnose it before your next test — start with the downstream sensor and check for contamination and wiring issues.

What contaminates a downstream oxygen sensor?

Oil or coolant burning in the exhaust from internal engine wear, silicone from the wrong sealant used upstream, and raw fuel from a rich-running event all coat the sensing element. Once contaminated, the sensor can stick to one side and stop switching.

OBD-II trouble code

P2273: O2 Sensor Signal Stuck Rich (Bank 2, Sensor 2)

The downstream oxygen sensor on Bank 2 — behind the catalytic converter — is reporting a signal stuck toward rich. It's the Bank 2 mirror of P2271 and mainly an emissions code; the car almost always drives normally.

Quick facts

System: Powertrain
Category: Oxygen Sensor
Severity: Low severity
Drivable: Usually safe to drive short-term
Repair cost range: $150 – $400
DIY difficulty: Intermediate DIY

What does P2273 mean?

This code is the Bank 2 counterpart of P2271. The downstream oxygen (O2) sensor on Bank 2 sits behind that bank's catalytic converter and monitors catalyst efficiency rather than doing primary fuel control. On a healthy system its signal is fairly steady and mid-range because the catalyst buffers the oxygen swings.

P2273 sets when the Bank 2 downstream sensor signal stays biased or stuck toward the rich side — a high, flat voltage above roughly 0.8 volts — instead of tracking the way the engine control module (ECM) expects. It's a rationality fault: the circuit is intact, but the reading is stuck and no longer plausible.

"Bank 2" is the side of a V-configured engine that does not contain cylinder 1; inline engines have only Bank 1 and never set P2273. "Sensor 2" is the downstream sensor. Because this sensor does little fuel trimming, P2273 rarely affects driveability. The usual cause is an aged or contaminated downstream sensor stuck high — oil or coolant in the exhaust, or a prior rich-running event, can bias it rich. Less often the reading is accurate and Bank 2 or its catalyst really is running rich, in which case upstream fuel-trim or catalyst codes usually appear alongside it.

Common causes

Aged or contaminated downstream Bank 2 oxygen sensor stuck high (most common)
Oil or coolant contamination in the Bank 2 exhaust coating the sensor
Residual rich-running event that saturated the sensor
Damaged, chafed, or corroded downstream sensor wiring or connector
Sensor heater fault slowing response
Genuine rich exhaust from a Bank 2 fueling problem (usually with other codes)

Symptoms

Check engine light is on
Almost never any driveability symptom
Failed emissions inspection
Possible companion fuel-trim or catalyst codes
Slight fuel smell only if the engine is genuinely rich

Diagnostic steps

1.Scan for all codes. Companion upstream rich codes (P0175) or a Bank 2 catalyst code point to a real rich condition rather than just the sensor.
2.Monitor Bank 2 Sensor 2 voltage live and compare with Bank 1. With P2273 the Bank 2 rear signal sits high and flat.
3.Inspect the sensor and wiring for oil or coolant contamination and connector corrosion.
4.Confirm the engine is not genuinely running rich by checking upstream sensor behavior and fuel trims.
5.Check the sensor heater circuit if the signal is slow to respond.
6.If the engine fueling is correct and wiring is good, replace the downstream Bank 2 sensor.

Repair cost

$150 – $400

Downstream oxygen sensor replacement runs about $150 to $400 in parts and labor, with the sensor itself typically $40 to $150. If the code turns out to be caused by a genuinely rich engine, the cost tracks that underlying repair rather than the sensor.

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.

Estimate your repair cost

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.