OBD CodesWhat it means
The first oxygen sensor sits in the exhaust before the catalytic converter. It tells the computer whether the engine is burning too much or too little fuel, many times a second, and the computer trims the fuel to match. A slow, stuck or dead sensor leaves the engine guessing.
Codes in this group
| Code | Meaning |
|---|---|
| P0130 | Oxygen sensor circuit fault, bank 1 sensor 1 |
| P0131 | Oxygen sensor voltage low, bank 1 sensor 1 |
| P0132 | Oxygen sensor voltage high, bank 1 sensor 1 |
| P0133 | Oxygen sensor slow to respond, bank 1 sensor 1 |
| P0134 | Oxygen sensor shows no activity, bank 1 sensor 1 |
| P0150 | Oxygen sensor circuit fault, bank 2 sensor 1 |
| P0151 | Oxygen sensor voltage low, bank 2 sensor 1 |
| P0152 | Oxygen sensor voltage high, bank 2 sensor 1 |
| P0153 | Oxygen sensor slow to respond, bank 2 sensor 1 |
| P0154 | Oxygen sensor shows no activity, bank 2 sensor 1 |
| P2195 | Oxygen sensor stuck lean, bank 1 sensor 1 |
| P2196 | Oxygen sensor stuck rich, bank 1 sensor 1 |
| P2197 | Oxygen sensor stuck lean, bank 2 sensor 1 |
| P2198 | Oxygen sensor stuck rich, bank 2 sensor 1 |
| P2A00 | Oxygen sensor reading out of range, bank 1 sensor 1 |
| P2A03 | Oxygen sensor reading out of range, bank 2 sensor 1 |
Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.
What you may notice
- Higher fuel use
- Rough idle or slight hesitation
- Failed emission test
- Often no symptom at all besides the warning light
Common causes
Most likely first:
- An old sensor: they wear out with age and distance
- An exhaust leak near the sensor
- Contamination from coolant or oil being burnt
- Wiring damaged by exhaust heat
- A real mixture problem, such as a vacuum leak or leaking injector
What to check first
- Listen for a ticking exhaust leak near the engine when cold
- Check if lean or rich codes (P0171, P0172) are stored too: fix those first
- A workshop can watch the sensor switching on a scan tool before replacing it
Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.
After the repair
Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.
Related codes
Mass air flow (MAF) sensor (P0100), Manifold pressure (MAP) and barometric sensor (P0105), Intake air temperature sensor (P0110), Engine coolant temperature sensor (P0115), Thermostat and engine warm-up (P0125), Throttle position sensor (P0120), Accelerator pedal sensor and throttle agreement (P2120), Electronic throttle actuator (P2100). All codes.
Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.