P0031
Fix within 1-2 weeksThe front oxygen sensor on Bank 1 has a low voltage condition in its heater circuit, meaning the sensor isn't heating up properly.
Code P0031 means your front oxygen sensor's heater isn't working. Common causes: Faulty O2 sensor (80%), wiring issues (15%), blown fuse (4%). Drivability: Yes, safe to drive. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0031?
Yes, safe to drive
No restrictions, but fix within 1-2 weeks to avoid long-term issues and poor fuel economy.
Stop driving immediately if: Flashing CEL (indicates misfire, not typical for P0031 alone), burning smell, significant power loss.
Symptoms of P0031
- 1Check Engine Light is on
- 2Reduced fuel economy
- 3Engine may run slightly rough or hesitate (less common)
- 4Vehicle will fail an emissions test
Common Causes of P0031
Parts most likely causing this code, ranked by probability
The internal heater element within the oxygen sensor has failed, preventing it from reaching operating temperature quickly to provide accurate exhaust gas readings.
80% of P0031 cases are fixed by replacing this part
A short to ground, an open circuit, or corrosion in the wiring leading to the Bank 1 Sensor 1 oxygen sensor heater prevents proper voltage delivery.
15% of P0031 cases are fixed by repairing the wiring
A fuse protecting the oxygen sensor heater circuit has blown, cutting off power to the sensor's heater.
4% of P0031 cases are fixed by replacing a fuse
A rare internal fault within the engine computer prevents it from properly controlling or powering the oxygen sensor heater circuit.
1% of P0031 cases are fixed by replacing the PCM
Check These First (Before Buying Parts)
- Check the fuse for the oxygen sensor heater circuit in your vehicle's fuse box.
- Visually inspect the wiring harness leading to the Bank 1 Sensor 1 oxygen sensor for any cuts, fraying, or corrosion.
How to Diagnose P0031
- 1Check the fuse box for any blown fuses related to the O2 sensor heaters.
- 2Visually inspect the wiring harness and connector for the Bank 1 Sensor 1 oxygen sensor for any signs of damage, corrosion, or loose connections.
- 3Using a multimeter, check for proper voltage supply to the oxygen sensor heater circuit at the sensor connector.
- 4Disconnect the oxygen sensor and measure the resistance of the heater element across the appropriate pins. Compare to factory specifications.
- 5If voltage and wiring are good, and the sensor's heater resistance is out of spec, replace the Bank 1 Sensor 1 oxygen sensor.
P0031 on Popular Vehicles
Toyota Camry
2007-2024P0031 on a Camry is almost always a failed Bank 1 Sensor 1 oxygen sensor. The sensor is usually accessible from under the hood or underneath the vehicle.
85% fixed by replacing the oxygen sensor
Honda Accord
2003-2024For Honda Accords, P0031 typically points to a faulty upstream oxygen sensor. Check the wiring carefully as Honda harnesses can sometimes be prone to rodent damage or corrosion near the exhaust.
75% fixed by replacing the oxygen sensor, 15% by wiring repair
Ford F-150
2004-2024P0031 on an F-150 is a common oxygen sensor failure. The front O2 sensors are often located in the exhaust manifold, which can make removal challenging if seized.
80% fixed by replacing the oxygen sensor
Frequently Asked Questions
What does P0031 mean?
P0031 indicates that the heater circuit for your upstream (pre-catalytic converter) oxygen sensor on Bank 1 has a low voltage condition, meaning the sensor isn't heating up as it should.
Can I drive with P0031?
Yes, you can drive safely with P0031. Your engine will likely run in "open loop" mode, which means it won't be optimizing fuel delivery based on exhaust gases. This will cause reduced fuel economy and increased emissions, but it won't immediately damage your engine.
Will P0031 clear itself?
No, P0031 will not clear itself. The engine computer detects a persistent fault in the heater circuit. The code will remain until the underlying issue is diagnosed and repaired.
How do I fix P0031 myself?
Start by checking the relevant fuse. Then, inspect the wiring to the Bank 1 Sensor 1 oxygen sensor for damage. If those are good, you'll likely need to replace the oxygen sensor itself.
How much does it cost to fix P0031?
A DIY fix typically costs $50-$200 for a new oxygen sensor. Professional repair at a shop will cost $150-$500, including parts and labor.
P0031 keeps coming back - why?
If P0031 returns, it's often due to an overlooked wiring issue, a faulty replacement sensor, or a deeper electrical problem that wasn't fully diagnosed. Double-check the wiring harness thoroughly.
Will P0031 fail emissions/smog test?
Yes, P0031 will cause your vehicle to fail an emissions or smog test. The oxygen sensor is a critical component of the emissions control system, and a fault in its heater circuit prevents it from functioning correctly.
What's the difference between P0031 and P0135?
P0031 specifically indicates a "low voltage" condition in the heater circuit, while P0135 is a more general "heater circuit malfunction." Both point to an issue with the Bank 1 Sensor 1 oxygen sensor's heater, but P0031 is more specific about the nature of the electrical fault.
P0031 on Ford F-150?
On Ford F-150s, P0031 is commonly caused by a failed Bank 1 Sensor 1 oxygen sensor. The sensor can be difficult to access due to its location on the exhaust manifold, but it's a straightforward replacement once you get to it.
Questions to Ask Your Mechanic
Did you check the fuse for the O2 sensor heater circuit, and did you test the voltage at the sensor connector before recommending a replacement?
Good answer: Yes, I confirmed the fuse is good, and I measured 12V at the connector. The sensor's heater resistance was out of spec, confirming the sensor itself is faulty.
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 basic electrical testing with a multimeter and potentially an O2 sensor socket, which can be tricky to use in tight spaces.
Cost of Waiting
Ignoring P0031 will lead to consistently poor fuel economy and increased emissions. Over a long period, the engine running rich or lean due to inaccurate O2 readings can potentially damage your catalytic converter, turning a $50-$200 sensor job into a $800-$2,500 converter replacement.
While You're In There...
If you're removing exhaust components to access the sensor, replacing old gaskets prevents exhaust leaks.
Applying anti-seize to the new O2 sensor threads prevents it from seizing in the exhaust, making future removal easier.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- O2 sensor socket (7/8" or 22mm)
- Ratchet and extensions
- Wire brush (for exhaust threads)
- Anti-seize compound
P0031 is a very common code, and in most cases, it's a straightforward fix involving replacing the oxygen sensor. Your engine will run much more efficiently afterward.
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Your Next Steps
Step 1: Check the fuse for the O2 sensor heater circuit. Consult your vehicle's owner's manual for the exact fuse location.
Step 2: If the fuse is good, visually inspect the wiring and connector for the Bank 1 Sensor 1 oxygen sensor. Look for any damage, corrosion, or loose pins.
Step 3: If wiring looks good, use a multimeter to test for voltage at the sensor connector and the resistance of the heater element within the sensor itself. If the sensor's resistance is out of specification, it's faulty.