P0151
Fix within 1-2 weeksThe oxygen sensor on Bank 2, Sensor 1 is reporting a consistently low voltage, indicating a lean condition or a sensor malfunction.
Code P0151 means your Bank 2 Sensor 1 oxygen sensor reports low voltage. Common causes: Faulty O2 sensor (70%), exhaust leak (15%), wiring issues (10%). Drivability: Yes, safe to drive. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0151?
Yes, safe to drive
No restrictions, but fix within 1-2 weeks to prevent further issues.
Stop driving immediately if: Flashing Check Engine Light, significant power loss, loud exhaust noises, or a strong rotten egg smell from the exhaust.
Symptoms of P0151
- 1Check Engine Light is on
- 2Reduced fuel economy
- 3Engine may run rough or hesitate
- 4Engine may lack power
Common Causes of P0151
Parts most likely causing this code, ranked by probability
The oxygen sensor itself is faulty and sending an incorrect low voltage signal to the engine computer.
70% of P0151 cases are fixed by replacing this part
An exhaust leak near the Bank 2 Sensor 1 allows unmetered air into the exhaust stream, causing the sensor to falsely read a lean condition.
15% of P0151 cases are fixed by repairing this part
Damaged wiring, a corroded connector, or a loose connection to the oxygen sensor can disrupt the signal, causing a low voltage reading.
10% of P0151 cases are fixed by repairing this part
A significant vacuum leak or a problem with fuel delivery (like a clogged injector or low fuel pressure) can cause a genuine lean condition that the sensor accurately reports.
5% of P0151 cases are fixed by repairing this part
Check These First (Before Buying Parts)
- Visually inspect the Bank 2 Sensor 1 oxygen sensor and its electrical connector for any obvious damage, frayed wires, or corrosion.
- Listen carefully for any hissing or ticking sounds from the exhaust system, especially near the sensor, which could indicate an exhaust leak.
How to Diagnose P0151
- 1Visually inspect the Bank 2 Sensor 1 oxygen sensor and its wiring for damage, corrosion, or loose connections.
- 2Check for exhaust leaks near the Bank 2 Sensor 1 by listening for hissing sounds or using a smoke machine.
- 3Use an OBD-II scan tool to monitor live data for Bank 2 Sensor 1 voltage and compare it to Bank 1 Sensor 1 (if applicable) to confirm the low reading.
- 4Check fuel trims (short term and long term) for Bank 2 to see if the engine computer is trying to compensate for a lean condition.
- 5Test the oxygen sensor heater circuit for proper resistance and voltage supply.
- 6If all other checks are inconclusive, consider testing the oxygen sensor's signal output directly with a multimeter.
P0151 on Popular Vehicles
Toyota Camry
2007-2024Oxygen sensor failures, particularly upstream sensors, are a common wear item on these vehicles around 100,000-150,000 miles. Bank 2 Sensor 1 is typically accessible.
75% fixed by replacing this part
Honda Accord
2003-2024Similar to Toyota, Honda Accords frequently experience oxygen sensor failures as they age. Wiring integrity should also be checked, as rodent damage can occur.
70% fixed by replacing the O2 sensor
Ford F-150
2004-2024Ford F-150s are known for exhaust manifold leaks, especially on older models or those with high mileage. These leaks, if near the Bank 2 Sensor 1, will cause a P0151 code. Always inspect for leaks first.
60% fixed by replacing the O2 sensor, 25% by fixing exhaust leak
Frequently Asked Questions
What does P0151 mean?
P0151 indicates that the upstream oxygen sensor on Bank 2 (the side of the engine without cylinder #1) is consistently sending a low voltage signal to the engine computer. This suggests a lean air-fuel mixture or a problem with the sensor itself.
Can I drive with P0151?
Yes, you can drive safely with a P0151 code. However, you should fix it within 1-2 weeks. Ignoring it will lead to reduced fuel economy and increased emissions. A prolonged lean condition can also cause engine damage or catalytic converter failure.
Will P0151 clear itself?
No, P0151 will not clear itself. The engine computer detects a persistent fault with the oxygen sensor's voltage. You must diagnose and repair the underlying issue, then clear the code with a scan tool.
How do I fix P0151 myself?
Start by visually inspecting the Bank 2 Sensor 1 oxygen sensor and its wiring. Check for exhaust leaks near the sensor. If no obvious issues are found, use a scan tool to confirm the sensor's voltage reading. If the sensor is consistently low, replacing the Bank 2 Sensor 1 oxygen sensor is the most common fix.
How much does it cost to fix P0151?
A DIY fix for P0151, primarily replacing the oxygen sensor, costs $50-$200 for the part. Professional repair at a shop typically costs $150-$500, including parts and labor.
P0151 keeps coming back - why?
If P0151 keeps returning, it means the root cause was not addressed. This often happens if you replaced the O2 sensor but an exhaust leak, wiring issue, or an actual lean condition (like a vacuum leak or fuel delivery problem) was the true culprit. A thorough diagnosis with a scan tool is necessary.
Will P0151 fail emissions/smog test?
Yes, P0151 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on is an automatic failure, and the underlying issue directly impacts exhaust emissions.
What's the difference between P0151 and P0174?
P0151 specifically indicates a low voltage signal from the Bank 2 Sensor 1 oxygen sensor, suggesting a sensor fault or a lean condition. P0174 means the engine computer has detected a 'System Too Lean' condition on Bank 2, indicating that the engine is actually running lean. P0151 can be a cause of P0174, or they can appear together if the sensor is accurately reporting a lean condition.
P0151 on Ford F-150?
On Ford F-150s, P0151 is often caused by a faulty Bank 2 Sensor 1 oxygen sensor. However, exhaust manifold leaks are also common on these trucks and can cause a false lean reading, triggering P0151. Always check for exhaust leaks before replacing the sensor.
Questions to Ask Your Mechanic
Did you check for exhaust leaks near the Bank 2 Sensor 1 before recommending an O2 sensor replacement?
Good answer: Yes, I performed a visual inspection and listened for leaks. I also used a smoke machine to confirm no leaks are present that could affect the sensor reading.
What were the live data readings for Bank 2 Sensor 1 voltage and fuel trims?
Good answer: Bank 2 Sensor 1 voltage was consistently below 0.1V, and the long-term fuel trims for Bank 2 were significantly positive, indicating the computer was adding fuel to compensate for a lean condition.
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-2 hours
Intermediate - requires a scan tool for proper diagnosis and an O2 sensor socket for removal, but the physical replacement is generally accessible.
Cost of Waiting
Ignoring P0151 will lead to continued poor fuel economy and increased harmful emissions. A persistent lean condition can cause engine misfires, overheat and damage your catalytic converter (a $800-$2,500 repair), or even lead to internal engine damage over time. A $50-$200 oxygen sensor replacement now prevents a much larger bill later.
While You're In There...
If you find an exhaust leak, replacing the relevant exhaust gaskets at the same time as the O2 sensor saves labor and prevents future leaks.
Applying anti-seize to the threads of the new O2 sensor prevents it from seizing in the exhaust pipe, making future removal much easier.
Tools You'll Need
- OBD-II Scan Tool
- Oxygen Sensor Socket (7/8 inch or 22mm)
- Ratchet and extensions
- Wrench set
- Wire brush (for cleaning threads)
- Multimeter (for advanced diagnostics)
P0151 is a common code, and in most cases, it's a straightforward fix involving replacing the oxygen sensor. Your engine will run more efficiently and cleanly once repaired.
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Your Next Steps
Step 1: Perform a thorough visual inspection of the Bank 2 Sensor 1 oxygen sensor, its wiring harness, and the surrounding exhaust for any damage or leaks.
Step 2: Use an OBD-II scan tool to monitor the live data for Bank 2 Sensor 1 voltage. Compare it to Bank 1 Sensor 1 if your vehicle has two banks. If the voltage is consistently low (near 0V) and doesn't fluctuate, the sensor is likely faulty.
Step 3: If the sensor appears faulty after diagnostics, you'll likely need a new Bank 2 Sensor 1 oxygen sensor. Ensure you get the correct upstream sensor for your specific vehicle.