What Does P2271 Mean?
The downstream oxygen sensor on Bank 1 is reading consistently rich or stuck reading rich values. This indicates either sensor failure or an actual rich exhaust condition that could damage the catalytic converter.
Common Causes
45%
Failed or contaminated Bank 1 Sensor 2 oxygen sensor
20%
Excessive fuel pressure causing rich condition
15%
Leaking fuel injectors creating rich exhaust
12%
Damaged oxygen sensor wiring or connector
8%
Faulty Mass Air Flow sensor causing over-fueling
Diagnostic Steps
1
Step 1: Monitor live oxygen sensor voltage for Bank 1 Sensor 2; verify stuck rich reading (typically above 0.55V continuously)
2
Step 2: Check fuel pressure at rail; compare to specifications for overpressure condition
3
Step 3: Monitor fuel trims; excessive negative long-term trim indicates actual rich condition
4
Step 4: Test oxygen sensor response by creating lean condition; observe if voltage drops appropriately
5
Step 5: If fuel system is normal and sensor doesn't respond, replace Bank 1 Sensor 2 oxygen sensor
Estimated Repair Cost
$150 - $500
Parts + labor, varies by vehicle and location
The downstream oxygen sensor on Bank 1 is reading consistently rich or stuck reading rich values. This indicates either sensor failure or an actual rich exhaust condition that could damage the catalytic converter.
The most common cause of P2271 (O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2) is: Failed or contaminated Bank 1 Sensor 2 oxygen sensor
Typical repair costs for P2271 range from $150 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive short-term but can damage catalytic converter due to excessive unburned fuel. May reduce fuel economy significantly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2271 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control / Fuel System
Difficulty
Type
Generic (SAE)
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