Big Daddy said:
Sorry that is my fault. I deleted one when I saw that you had two dupicate posts. Maybe Gib will re-post his information for you.
Geez, you get an itchy trigger finger so I have to type it all over again.
Ok, here we go:
EGO. Exhaust Gas Oxygen Sensor, or O2 sensor, or Lambda Sensor.
What it does: Measures the amount of oxygen in the exhaust stream and sends a signal to the DME to adjust the fuel accordingly. Happens constantly, every few milliseconds.
What happens when it fails: Fuel economy suffers, emmissions go up, possibly causing rough running.
If the check engine light is on and you have narrowed it down to O2 sensor #1, that is for bank 1, or cylinders 1-3. It is either getting slow, has failed altogether, or the heater for it has failed.
They cannot be repaired, the are replaced. They are a common maintenance item and if one has failed, the other is not far behind. I would just replace both if they have never been done and you can afford it.
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