P0131: the front oxygen sensor signal is reading too low
The oxygen sensor sits in the exhaust before the catalytic converter and checks how much oxygen is left in the exhaust, which tells the engine control unit whether the fuel mixture needs more fuel or less. This code means the electrical signal from bank 1's sensor is reading lower than the range the computer will accept. With this signal out of range, the engine control unit falls back on a default value instead.
You might notice
- The engine warning light comes on
- Fuel use may creep up as the computer can no longer fine-tune the mixture from this sensor
- oxygen sensor
- — a sensor in the exhaust that measures how much oxygen is left after combustion
- bank 1
- — the side of the engine that has cylinder number 1
What the code itself says
P0131 is a powertrain (engine, gearbox and drive system) code, and the 0 after the letter means it is a generic code with a standard meaning.
Grouped here as: Engine running, fuelling and misfires — Air metering, fuelling, ignition, misfire, idle, boost, knock, oxygen sensors and the catalyst, all working together in the running engine. That grouping is ours, to help explain the code. The code's official family is the letter at the start.
This page is generic. Your car isn't.
A code on its own only tells you what the sensor saw, not what's actually wrong — and that changes next to your other codes. Read this one together with the rest of your scan and we'll work out what's really going on.
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