P0151
O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
- Severity
- Medium
- Driving
- Drivable — book it in
The upstream oxygen sensor on bank 2 is reporting a persistently low voltage. On these sensors low voltage means a lean signal - the sensor is saying there is more oxygen in the exhaust than expected. That can mean the mixture really is lean, or that the sensor circuit is shorted to ground, or that air is getting in through an exhaust leak.
Possible causes
- CommonExhaust leak ahead of the sensor letting fresh air in
- CommonSensor signal wire shorted to ground
- CommonGenuinely lean mixture - vacuum leak or weak fuel delivery
- PossibleFailed oxygen sensor
- PossibleCorroded or water-ingressed connector
What you might notice
- Check engine light on
- Hesitation or stumble under acceleration
- Rough idle
- Worse fuel economy
What to check, in order
- Look for exhaust leaks between the engine and this sensor first. This is the most common cause and does not require replacing anything.
- Check the fuel trim values. If trim is strongly positive, the mixture really is lean and the sensor is telling the truth - fix the lean condition, not the sensor.
- Inspect the sensor wiring for chafing against the exhaust or bodywork, which can short the signal wire to ground.
- Check the connector for water ingress and green corrosion on the pins.
- Only replace the sensor once leaks, wiring and a genuine lean condition have been ruled out.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Fuel and air metering
P0100P0101P0102P0103P0104P0105P0106P0107P0108P0109P0110P0111P0112P0113P0114P0115P0116P0117P0118P0119P0120P0121P0122P0123P0124P0125P0126P0127P0128P0129P0130P0131P0132P0133P0134P0135P0136P0137P0138P0139P0140P0141P0142P0143P0144P0145P0146P0147P0148P0149P0150P0151P0152P0153P0154P0155P0156P0157P0158P0159P0160P0161P0162P0163P0164P0165P0166P0167P0168P0169P0170P0171P0172P0173P0174P0175P0176P0177P0178P0179P0180P0181P0182P0183P0184P0185P0186P0187P0188P0189P0190P0191P0192P0193P0194P0195P0196P0197P0198P0199