O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
The front lambda sensor, ahead of the catalyst, measures the oxygen left in the exhaust. With it the ECU corrects the air–fuel mixture several times a second.
What the car has detected
The front sensor takes too long to react to mixture changes: it is usually worn or contaminated.
It is not dangerous, but the car may use more fuel and fail the inspection. Have it checked when you can.
Symptoms
- Engine warning light on
- Higher fuel use
- May fail the emissions test
Possible causes
- Worn, contaminated or faulty lambda sensor
- Exhaust leak ahead of the sensor
- Air leak in the intake or the crankcase breather
- Burnt oil or coolant fouling the sensor
Checks for the garage
- Check in live data how fast the sensor switches
- Look for exhaust leaks
- Look for air leaks in the intake
Next step
Ask for the lambda sensor wiring and the sensor to be checked before it is replaced, and for exhaust leaks to be looked for.
You can keep using the car and book a visit without hurry.