P0157
Fix within 1-2 weeksThe oxygen sensor after the catalytic converter on Bank 2 is reporting consistently low voltage, indicating a lean condition or a faulty sensor.
Code P0157 means the downstream oxygen sensor on Bank 2 has low voltage. Common causes: Faulty O2 sensor (80%), exhaust leak (10%), wiring issues (8%). Drivability: Yes, safe to drive. Repair cost: $100-$250 DIY, $200-$500 professional.
Can I Drive With P0157?
Yes, safe to drive
No restrictions, but fix within 1-2 weeks to avoid long-term issues and maintain fuel economy.
Stop driving immediately if: Flashing CEL, loud noises from the exhaust, burning smell, or significant power loss (which are not typical for P0157 alone).
Symptoms of P0157
- 1Check Engine Light is on
- 2Slight decrease in fuel economy (often unnoticeable)
- 3Engine may run slightly rough (rare)
Common Causes of P0157
Parts most likely causing this code, ranked by probability
The downstream oxygen sensor itself has failed and is no longer accurately reporting exhaust oxygen levels, causing a low voltage reading.
80% of P0157 cases are fixed by replacing this part
An exhaust leak near the Bank 2 Sensor 2 can allow outside air to enter the exhaust stream, causing the sensor to incorrectly read a lean condition (low voltage).
10% of P0157 cases are fixed by repairing an exhaust leak
Damaged, corroded, or loose wiring and connectors to the Bank 2 Sensor 2 can prevent the sensor from sending a proper voltage signal to the engine computer.
8% of P0157 cases are fixed by repairing wiring
A rare internal fault within the engine computer can cause it to misinterpret or incorrectly process the oxygen sensor's signal.
2% of P0157 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the Bank 2 Sensor 2 wiring for any cuts, fraying, or signs of rodent damage.
- Check the O2 sensor connector for corrosion or loose pins.
- Listen for any exhaust leaks near the sensor, especially when the engine is cold and first started.
How to Diagnose P0157
- 1Visually inspect the Bank 2 Sensor 2 wiring and connector for damage, corrosion, or loose connections.
- 2Inspect the exhaust system around Bank 2 Sensor 2 for any signs of leaks (soot, rust, or audible hissing).
- 3Use an OBD-II scan tool to monitor live data from Bank 2 Sensor 2; look for a consistently low voltage reading (under 0.1V) that does not fluctuate.
- 4If possible, use a multimeter to test the O2 sensor's heater circuit and signal wire for proper voltage and resistance.
- 5If all other checks are inconclusive, consider replacing the Bank 2 Sensor 2 oxygen sensor.
P0157 on Popular Vehicles
Ford F-150
2004-2024Bank 2 Sensor 2 on F-150s is often exposed to road debris and corrosion, leading to premature failure. Exhaust leaks are also common on these trucks, especially at manifold or flange connections.
85% fixed by replacing O2 sensor or repairing exhaust
Toyota Camry
2007-2024On V6 Camry models, Bank 2 Sensor 2 is typically accessible but can be tight. Sensor failure is the primary cause, but check for exhaust leaks around the rear catalytic converter.
80% fixed by replacing O2 sensor
Honda Accord
2003-2024For V6 Accord models, Bank 2 Sensor 2 is usually located after the rear catalytic converter. Wiring damage from road debris or corrosion is a slightly more common issue here, alongside sensor failure.
82% fixed by replacing O2 sensor or repairing wiring
Frequently Asked Questions
What does P0157 mean?
P0157 indicates that the oxygen sensor located after the catalytic converter on Bank 2 (the side of the engine without cylinder #1) is reporting a consistently low voltage signal to the engine's computer. This suggests the sensor is faulty or the exhaust is running lean.
Can I drive with P0157?
Yes, you can drive safely with a P0157 code. This code typically does not indicate an immediate risk of engine damage. However, it affects your vehicle's emissions and fuel economy, so fix it within 1-2 weeks.
Will P0157 clear itself?
No, P0157 will not clear itself. The engine computer will continue to detect the low voltage condition from the oxygen sensor. You need to diagnose and fix the underlying issue, then clear the code with an OBD-II scanner.
How do I fix P0157 myself?
Start by inspecting the Bank 2 Sensor 2 wiring and exhaust for leaks. If those are fine, the most common fix is replacing the Bank 2 Sensor 2 oxygen sensor. You'll need an O2 sensor socket and a wrench.
How much does it cost to fix P0157?
DIY repair costs for P0157 are typically $100-$250 for a new oxygen sensor. Professional repair at a shop usually costs $200-$500, including parts and labor.
P0157 keeps coming back - why?
If P0157 keeps returning, it often means the initial diagnosis was incomplete. Double-check for subtle exhaust leaks, thoroughly inspect the wiring for intermittent issues, or ensure the replacement O2 sensor is a quality part and installed correctly. In rare cases, a failing catalytic converter or PCM could be the cause.
Will P0157 fail emissions/smog test?
Yes, P0157 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on automatically fails the test, and the underlying issue with the oxygen sensor directly impacts the vehicle's emissions control system.
What's the difference between P0157 and P0158?
P0157 indicates a consistently low voltage from Bank 2 Sensor 2, suggesting a lean condition or a dead sensor. P0158 indicates a consistently high voltage from Bank 2 Sensor 2, suggesting a rich condition or a short to voltage in the sensor circuit.
P0157 on Ford F-150
On Ford F-150s, P0157 is commonly caused by a failing Bank 2 Sensor 2 oxygen sensor, especially on higher mileage vehicles. Exhaust leaks are also a common culprit due to the truck's exhaust routing and exposure. Always check for leaks first, then replace the sensor.
Questions to Ask Your Mechanic
Did you check for exhaust leaks near the Bank 2 Sensor 2 before recommending an O2 sensor replacement?
Good answer: Yes, I visually inspected the exhaust system and used a smoke machine/listened for leaks around the sensor and found no issues.
What were the live data readings for Bank 2 Sensor 2, specifically the voltage, and how did they compare to Bank 1 Sensor 2?
Good answer: Bank 2 Sensor 2 was stuck at 0.05V, while Bank 1 Sensor 2 was cycling normally between 0.1V and 0.9V, indicating a clear fault with Bank 2 Sensor 2.
Repair Cost Estimate
DIY Repair
Parts only
$100-$250
Shop Repair
Parts + labor
$200-$500
Save $100-$250 by doing it yourself
Difficulty
intermediate
Time
1-2 hours
Intermediate - requires an OBD-II scan tool for diagnosis and specific tools like an O2 sensor socket for replacement. Access to the sensor can be challenging on some vehicles.
Cost of Waiting
Ignoring P0157 can lead to reduced fuel economy and increased emissions. While it won't immediately damage your engine, prolonged incorrect fuel trim adjustments can put additional stress on your catalytic converter, potentially shortening its lifespan. A $150 O2 sensor fix now prevents a $1,000-$2,500 catalytic converter replacement later.
While You're In There...
If you find an exhaust leak, replacing nearby gaskets is essential to ensure a proper seal and prevent future leaks.
Applying anti-seize to the new O2 sensor threads prevents it from seizing in the exhaust pipe, making future removal much easier.
Tools You'll Need
- OBD-II Scan Tool
- O2 Sensor Socket (7/8 inch or 22mm)
- Ratchet and extensions
- Wrench set
- Wire brush (for cleaning threads)
- Anti-seize compound
P0157 is a common emissions code, usually indicating a failing oxygen sensor. The repair is straightforward for most DIYers, and your vehicle will run more efficiently afterward.
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Your Next Steps
Step 1: Visually inspect the Bank 2 Sensor 2 wiring and exhaust system for any obvious damage or leaks. Look for soot around exhaust joints.
Step 2: If no visual issues are found, use an OBD-II scan tool to confirm the low voltage reading from Bank 2 Sensor 2. Compare it to Bank 1 Sensor 2 if your vehicle has two banks.
Step 3: If the sensor is confirmed to be faulty, purchase a new Bank 2 Sensor 2 oxygen sensor. You'll likely need an O2 sensor socket for removal and installation.