P0131 means the upstream oxygen sensor on bank 1 is consistently reporting a low voltage, indicating a lean exhaust condition. The ECU may compensate by adding extra fuel, causing rich running. This code often points to a failing O2 sensor or an actual lean condition.
DTC/P0131·Toyota
P0131 on Toyota: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Toyota
P0131 on a Toyota means the upstream oxygen sensor on bank 1 is consistently reporting a low voltage, indicating a lean exhaust condition. The ECU may compensate by adding extra fuel, causing rich running. This code often points to a failing O2 sensor or an actual lean condition.
Repair cost on Toyota€41 - €252
What does P0131 mean on a Toyota?
Toyota Corolla
2005-2024The 1ZR-FE and 2ZR-FE engines are reliable, but O2 sensors typically need replacement around 120,000-150,000 km. Use a Denso sensor (OE supplier) for best compatibility. The upstream sensor is easily accessible on the exhaust manifold.
What causes P0131 on a Toyota?
Beyond the generic causes listed on the main P0131 page, these are the Toyota-specific patterns we see most often:
Toyota CorollaO2 sensor degradation at high mileage
Toyota CorollaExhaust manifold cracking on older models causing false lean readings
How to diagnose P0131 on a Toyota with OBD2
Follow these steps to pinpoint the root cause of P0131:
- Use a scan tool to monitor the bank 1 sensor 1 O2 voltage in real time. A healthy sensor oscillates between 0.1V and 0.9V. A stuck-low reading (below 0.2V) suggests a lean condition or sensor failure
- Check for vacuum leaks by performing a smoke test or spraying propane around intake manifold gaskets, vacuum hoses, and the brake booster line. A leak causes real lean conditions
- Inspect the exhaust system between the engine and the O2 sensor for leaks. Cracked exhaust manifolds or loose connections allow outside air to reach the sensor, giving false lean readings
- Inspect the O2 sensor connector and wiring for corrosion, heat damage, or rodent chewing. Repair any wiring faults found
- If no leaks or wiring issues are found, replace the O2 sensor. Sensors degrade over time and should be replaced every 100,000-150,000 km as maintenance
How much does P0131 cost to fix on a Toyota? (EUR)
Estimated repair costs on a Toyota (Toyota parts and labour typically run 10% below the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0131 on Toyota
These codes commonly cluster with P0131 on Toyota vehicles:
FAQ: P0131 on Toyota
What does P0131 mean?
P0131 means the upstream oxygen sensor on bank 1 is reading low voltage consistently, which the ECU interprets as a lean exhaust condition. This sensor is critical for fuel mixture control - when it fails, the engine cannot properly regulate the air-fuel ratio.
Can I drive with P0131?
Yes, for short distances. The ECU compensates by richening the fuel mixture, which increases fuel consumption and can damage the catalytic converter over time. Schedule a repair within a few days to prevent secondary damage.
How long does an O2 sensor last?
Most modern oxygen sensors last 100,000 to 150,000 km. However, exposure to coolant leaks, silicone sealants, or contaminated fuel can shorten their lifespan significantly. If your vehicle has high mileage and the original sensors, age is the likely cause.
Is P0131 the same as P0171?
No. P0131 specifically indicates the O2 sensor circuit is reading low voltage (a sensor-side problem). P0171 indicates the fuel system is actually running lean based on long-term fuel trims. However, both can appear together if there is a real lean condition.
Looking for the full P0131 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0131 guideSkanyx · Toyota
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