OBD codes / P2271
P2271
ModerateO2 Sensor Signal Stuck Rich (Bank 1, Sensor 2)
Fine to drive while you arrange the repair — the engine's fuel control does not run through this sensor. The one thing not to skip: rule out a genuine rich condition first, because sustained rich running is what actually destroys catalytic converters, and a stuck-rich downstream signal can be its symptom.
What this code means
P2271 is the rich-side counterpart of P2270: the post-catalyst sensor on bank 1 reports rich continuously and fails to show the behavior the computer expects behind a healthy converter. Because this sensor does not control fueling, the code seldom changes how the car drives; the question is why the signal is pegged. A failing or contaminated sensor and a signal wire shorted to voltage are the direct-fault explanations. The indirect one deserves a check too: an engine running genuinely rich pushes unburned fuel through the converter, which can hold the downstream signal high — so glance for upstream rich evidence like P0172 or P2196 before condemning the sensor. It overlaps with P0138 (high voltage on the same circuit), and like its lean twin it can distort catalyst monitoring until resolved.
Symptoms you might notice
- Check-engine light, usually with no driving change
- Failed emissions test
- Fuel smell or poor mileage only when a real rich condition is behind it
What it costs to fix
Typical range: $100–$450 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| O2 sensor (Bank 1, Sensor 2) | $30–$200 | ~0.3–1 hrs |
| Wiring or connector repair | $5–$60 | ~0.5–1.5 hrs |
| Exhaust leak repair (gasket or flange) | $15–$100 | ~0.5–1.5 hrs |
If the sensor is the fault, this is a routine, moderately priced job. The estimate does not cover the scenario where an upstream rich condition is the true cause — that diagnosis leads to fuel-system repairs priced under the relevant code, such as P0172.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P2271 for my exact vehicle →
Frequently asked
Should I check anything before replacing the sensor for P2271?
Yes — look for signs the engine is actually running rich: codes like P0172 or P2196, strongly negative fuel trims, a fuel smell, or fouled plugs. A downstream sensor honestly reporting fuel slipping through the converter is not broken, and replacing it would fix nothing.
What is the relationship between P2271 and P0138?
Both concern the bank 1 downstream sensor reading high. P0138 is triggered by circuit voltage above range; P2271 by the signal behaving stuck-rich during the monitoring routine. In practice the suspect list is the same — sensor, wiring short to voltage, or genuine rich exhaust.
Can P2271 cause a false catalytic converter failure?
It can interfere. The converter is graded by comparing upstream and downstream sensor behavior, and a downstream signal stuck rich corrupts that comparison — potentially triggering or masking a P0420. Fix this code first so the catalyst monitor judges the converter on real data.
My car drives perfectly — why fix this at all?
Three reasons: the check-engine light will mask any new problem that appears, an OBD emissions inspection is an automatic fail with the code active, and the computer currently cannot watch your catalytic converter — an expensive part you want monitored.
Seeing P2271 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P2271 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P2271 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.