P0140
Fix within 1-2 weeksYour engine computer isn't getting a signal from the oxygen sensor located after the catalytic converter on the first bank of cylinders.
Code P0140 means your downstream oxygen sensor isn't sending a signal. Common causes: Bad O2 sensor (70%), wiring issues (20%), exhaust leaks (5%). Drivability: Yes, safe to drive. Repair cost: $70-$180 DIY, $150-$500 professional.
Can I Drive With P0140?
Yes, safe to drive
No restrictions, but fix within 1-2 weeks to avoid long-term issues and failed inspections.
Stop driving immediately if: Flashing Check Engine Light (indicates a severe misfire), loud exhaust noises, or a strong rotten egg smell from the exhaust.
Symptoms of P0140
- 1Check Engine Light is on
- 2Slight decrease in fuel economy
- 3Failed emissions inspection
Common Causes of P0140
Parts most likely causing this code, ranked by probability
The oxygen sensor itself has failed and is no longer sending a signal to the engine computer.
70% of P0140 cases are fixed by replacing this part
Damaged, corroded, or disconnected wiring to the oxygen sensor prevents the signal from reaching the computer.
20% of P0140 cases are fixed by repairing wiring
An exhaust leak near the oxygen sensor can allow outside air in, causing the sensor to read incorrectly or show no activity.
5% of P0140 cases are fixed by repairing an exhaust leak
A rare internal fault in the engine computer can prevent it from properly reading the oxygen sensor signal.
5% of P0140 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the Bank 1 Sensor 2 oxygen sensor and its electrical connector for any obvious damage, corrosion, or disconnections.
- Check for any exhaust leaks near the oxygen sensor, as these can cause incorrect readings.
How to Diagnose P0140
- 1Visually inspect the Bank 1 Sensor 2 oxygen sensor and its wiring for any signs of damage, fraying, or corrosion.
- 2Check the electrical connector for the oxygen sensor to ensure it is securely plugged in and free of corrosion.
- 3Inspect the exhaust system near the sensor for any visible leaks, cracks, or loose connections.
- 4Use an OBD-II scan tool to monitor live data from the Bank 1 Sensor 2 oxygen sensor; look for a flat line at 0 volts or 0.45 volts.
- 5If visual inspection and live data confirm no activity, test the sensor's heater circuit and signal circuit with a multimeter.
- 6If the sensor tests bad and wiring is confirmed good, replace the oxygen sensor.
P0140 on Popular Vehicles
Honda Accord
2003-2024The downstream oxygen sensor (Bank 1 Sensor 2) is a common failure item on these models, especially after 100,000 miles. Replacement is usually straightforward.
75% fixed by replacing the O2 sensor
Toyota Camry
2007-2024Similar to Hondas, the downstream O2 sensor on Toyota Camrys is a common component to fail, leading to P0140. Check for exhaust leaks as well, as they can mimic sensor failure.
70% fixed by replacing the O2 sensor
Ford F-150
2004-2024On Ford F-150s, especially older models, O2 sensor failures are common. Also, inspect the wiring harness carefully for rodent damage or corrosion, which can be more prevalent on trucks.
65% fixed by replacing the O2 sensor
Frequently Asked Questions
What does P0140 mean?
P0140 indicates that your vehicle's engine computer is not detecting any activity or signal from the oxygen sensor located after the catalytic converter on the first bank of cylinders.
Can I drive with P0140?
Yes, you can drive safely with a P0140 code. This code primarily affects emissions and fuel economy, not immediate driveability. However, fix it within 1-2 weeks to prevent potential long-term issues.
Will P0140 clear itself?
No, P0140 will not clear itself. The engine computer needs to see a consistent, active signal from the oxygen sensor for a certain number of drive cycles before it will turn off the Check Engine Light. A faulty sensor or wiring will prevent this.
How do I fix P0140 myself?
Start by visually inspecting the oxygen sensor and its wiring for damage or disconnections. If they look good, use a scan tool to confirm the sensor is truly inactive. If it is, replacing the Bank 1 Sensor 2 oxygen sensor is the most common fix.
How much does it cost to fix P0140?
A DIY fix for P0140 typically costs $70-$180 for a new oxygen sensor and a specialized socket. Professional repair at a shop usually ranges from $150-$500, including parts and labor.
P0140 keeps coming back - why?
If P0140 keeps returning, it means the underlying issue wasn't fully resolved. Double-check for exhaust leaks, thoroughly inspect the wiring harness for hidden damage, or consider that the new sensor might be faulty. In rare cases, the engine computer itself could be the problem.
Will P0140 fail emissions/smog test?
Yes, P0140 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on, especially for an emissions-related sensor, is an automatic failure in most jurisdictions.
What's the difference between P0140 and P0136?
P0140 specifically means 'Oxygen Sensor Circuit No Activity Detected', indicating a complete lack of signal. P0136 means 'Oxygen Sensor Circuit Malfunction', which is a broader code indicating a general problem with the circuit, but not necessarily a complete lack of activity.
P0140 on Honda Accord?
P0140 is a common code on Honda Accords, particularly models with higher mileage. The downstream oxygen sensor (Bank 1 Sensor 2) is a frequent failure point. Replacing the sensor usually resolves the issue.
Questions to Ask Your Mechanic
Did you check the live data from the Bank 1 Sensor 2 oxygen sensor to confirm it's truly inactive?
Good answer: Yes, I hooked up the scan tool and confirmed the sensor is flat-lining at 0 volts, indicating no activity.
Have you inspected the wiring harness for any damage or corrosion leading to the sensor?
Good answer: Yes, I visually inspected the wiring and connector, and also performed a continuity test to ensure the circuit is intact.
Repair Cost Estimate
DIY Repair
Parts only
$70-$180
Shop Repair
Parts + labor
$150-$500
Save $80-$320 by doing it yourself
Difficulty
beginner
Time
0.5-1.5 hours
Beginner-friendly - Replacing an oxygen sensor is a common DIY task that requires basic hand tools and often a specialized oxygen sensor socket.
Cost of Waiting
Ignoring P0140 means your vehicle's emissions system isn't working correctly. You'll fail emissions tests and experience slightly reduced fuel economy. More critically, if the engine computer is running incorrect fuel trims due to the bad sensor, it can lead to premature wear or damage to your catalytic converter, turning a $100 sensor job into a $1,000-$2,500 converter replacement.
While You're In There...
If you need to remove any exhaust components to access the sensor, replacing old gaskets prevents future leaks and ensures a tight seal.
Applying anti-seize to the threads of the new oxygen sensor makes installation easier and prevents it from seizing in the exhaust pipe, simplifying future replacements.
Tools You'll Need
- OBD-II scan tool
- Wrench set or socket set
- Oxygen sensor socket
- Wire brush (optional, for exhaust threads)
- Anti-seize compound
P0140 is a very common code, usually indicating a simple sensor failure. Most repairs are straightforward and will get your vehicle running efficiently and passing emissions again.
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Your Next Steps
Step 1: Visually inspect the oxygen sensor's wiring and connector for any damage or loose connections. Also, check for any obvious exhaust leaks near the sensor.
Step 2: If the visual inspection doesn't reveal the problem, use an OBD-II scan tool to confirm the Bank 1 Sensor 2 oxygen sensor is indeed showing no activity in live data.
Step 3: If the sensor is inactive and wiring appears good, you'll likely need to replace the Bank 1 Sensor 2 oxygen sensor. You'll need an oxygen sensor socket for this.