0/2 sensor

03 Honda accord --computer says needs0/2 sensor–what does the sensor do?

The C o/2 sensor basically sniffs the exhaust coming out of your engine and tells the computer to make other sensors (Like idle position, MAS sensor, etc) richen or lean out the (Air vs. little air) fuel/air mixture that your cylinders burn off. In extreme cases the C o/2 sensor will make the car not run at all, or give you bad gas mileage. Depending on the manufacturer of the car, you will have to have that sensor replaced about every 25,000 miles to 45,000 miles. The sensor is not really, really expensive but it is usually in an inconvenient place and requires special tools.

There are two O2 sensors. The one ahead of the catalytic converter measures the oxygen content in the exhaust gas. From this the computer can trim the fuel ratio to the engine. The one after the catalytic converter measures the catalytic converters efficiency. So if it says sensor 1, it’s the one before the cat. If it says sensor 2, it’s the one after the cat.


While it is likely you do need to replace a sensor (see Tester’s response as to which one) I would like to point out that the computer is not saying you need to replace a sensor. It is saying it is getting signals from that sensor that don’t look right. Likely it is the sensor, but it could be a bad connection or some other odd thing. That is true of all those computer codes. They point towards something, but they don’t condemn them.

Beefy, I am curious about your source for that statement that O sensors need to be replaced every 25,000 to 45,000 miles. I am not an expert, so cannot negate that statement, just want to know if you have a source for it as part of my own learning process.

I think the O sensor and all the others cause the computer change the amount of fuel injected to the motor at each cycle of operation.

On my Toyota, the first sensor (called A/F sensor on the California certified models) failed, heater only, at 115,000 miles and the other one is still solid at 139,000 miles.

Doesn’t US law require those items relevant to smog controls to be warranteed a certain number of miles?

Its main mission is to help the computer to fine-tune the amount of fuel the engine needs/should get at steady engine speeds. When the throttle is moving, the throttle position sensor is the big boss of the operation. The engine temperature also helps and so does the mass airflow sensor. Generally, the O2 sensor was regarded as engine candy. The engine chews on them and spits em out by code when it’s done with them. Engines with problems will spit them out sooner than the good ones. Sometimes, the problem is in the wiring and will give you a hard time tracking it down.

Norm, Norm, Norm…what are we going to do with you? o2 sensors do not need regular maintenence or replacement intervals. Replace them when they go bad. Prices vary with the model but o2 sensors for a Taurus are about $80.00. Kind of steep.

how do you know it needs a new O2 sensor?

did you get the codes read?

what are the codes?

post the code here. dont abbreviate, or summarize. post the whole code here like P0123