Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is noticing that one of the oxygen sensors, which helps the engine run smoothly, is taking too long to respond. It's like a slow friend who doesn't react quickly when you call their name.
The P0139 code indicates that the oxygen sensor located in Bank 1, Sensor 2 is not responding as quickly as expected to changes in the exhaust gas composition.
An O2 sensor, or oxygen sensor, measures the amount of oxygen in the exhaust gases leaving the engine. The P0139 code is triggered when the sensor in Bank 1, Sensor 2 (downstream of the catalytic converter) does not respond quickly enough to changes in the air-fuel mixture. This slow response can affect the vehicle's emissions and fuel efficiency.
• Check Engine Light is on
• Increased fuel consumption
• Failed emissions test
• Faulty O2 sensor
• Exhaust leaks
• Wiring issues or poor electrical connections
O2 Sensor: A device that measures the amount of oxygen in the exhaust gases.
Bank 1: The side of the engine with cylinder 1, often the side where the first cylinder is located.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connections to the O2 sensor.
• Check for exhaust leaks near the sensor.
• Replace the faulty O2 sensor.
• Repair any exhaust leaks.
• Fix any wiring or connection issues.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $300
Moderate
• Toyota Camry
• Honda Accord
• Ford F-150
• Regularly inspect and maintain the exhaust system.
• Ensure timely replacement of oxygen sensors.
• Perform regular vehicle diagnostics.
Sensor Issue
• Have a professional mechanic inspect the vehicle if you're unsure.
• Do not ignore the Check Engine Light as it can lead to poor fuel economy.
Oxygen sensors may be covered under the vehicle's emissions warranty.
The P0139 code has been a common diagnostic trouble code since the introduction of OBD-II systems, often related to sensor aging or exhaust issues.
Moderate – While the vehicle may still be drivable, it is recommended to address this issue to avoid increased emissions and fuel consumption.
Driving with a faulty oxygen sensor can lead to increased emissions, which may not comply with local environmental regulations.
• Engine at operating temperature
• Vehicle running at steady speed
The O2 sensor for Bank 1 Sensor 2 is located downstream of the catalytic converter on the exhaust system.
Q: Can I drive with a P0139 code?
A: Yes, but it's best to fix it soon to avoid increased fuel consumption and emissions.
Q: How long does it take to replace an O2 sensor?
A: Replacing an O2 sensor typically takes about 1 to 2 hours.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.