OBD-II trouble code
P2272: O2 Sensor Signal Stuck Lean (Bank 2, Sensor 2)
The downstream oxygen sensor on Bank 2 — behind the catalytic converter — is reporting a signal stuck toward lean. It's the Bank 2 mirror of P2270 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
Browse every code in P2200–P22CA, or start from the full code library.
What does P2272 mean?
This code is the Bank 2 counterpart of P2270. 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. Its signal should be relatively steady and mid-range on a healthy system because the catalyst buffers the oxygen swings.
P2272 sets when the Bank 2 downstream sensor signal stays biased or stuck toward the lean side — a low, flat voltage — instead of behaving the way the engine control module (ECM) expects. It's a rationality fault: the circuit is electrically fine, 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 P2272. "Sensor 2" is the downstream sensor. Because this sensor does little or no fuel trimming, P2272 rarely affects driveability. Two causes account for most of these and they are worth taking in the right order. An exhaust leak near the rear Bank 2 sensor draws in outside air, which reads as oxygen and therefore as lean — a correct reading of a false environment, from a sensor with nothing wrong with it. An aged or contaminated sensor produces the same stuck-lean signal for real. Since a leak can make a healthy sensor look dead but a dead sensor cannot open a hole in your exhaust, check the pipework first. Less commonly the reading is accurate and the exhaust or catalyst on that bank is the real issue.
Common causes
- Exhaust leak near the rear Bank 2 sensor letting in outside air that reads lean — check this before condemning the sensor, because it produces an identical signal from a component that is working correctly
- Damaged, chafed, or corroded downstream sensor wiring or connector
- Aged or contaminated downstream Bank 2 oxygen sensor
- Sensor heater degraded, slowing response
- Moisture intrusion into the sensor connector
- Genuine post-catalyst lean reading from a Bank 2 exhaust or catalyst problem (less common)
Symptoms
- Check engine light is on
- Almost never any driveability symptom
- Failed emissions inspection
- Possible companion catalyst code such as P0430
- Slightly elevated tailpipe emissions in some cases
Diagnostic steps
- 1.Scan for all codes. A companion P0430 suggests inspecting the Bank 2 catalyst and exhaust rather than just the sensor.
- 2.Watch Bank 2 Sensor 2 voltage live and compare with Bank 1 Sensor 2. The downstream signal should be steady mid-range; with P2272 it sits low and flat.
- 3.Inspect the Bank 2 exhaust from the catalyst back for leaks, especially near the rear sensor bung. Let the exhaust cool before you put hands on it — a catalyst and the pipe behind it stay hot enough to burn long after the engine is switched off — and if the car has to come up to reach it, use a lift or axle stands rather than a jack.
- 4.Inspect the sensor connector and wiring for corrosion, chafing, or moisture.
- 5.Check the sensor heater circuit if the signal is slow to come alive after start-up.
- 6.If the exhaust is tight 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 typically $40 to $150. Access to the rear Bank 2 sensor varies by vehicle. Repairing a nearby exhaust leak adds $100 to $400 depending on what needs welding or replacing.
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.