P0133 Focus 1.8 Petrol Fault Code

[dhr90]

A couple of times last year the CEL came on, then went after 50 or so miles. Earlier this year I serviced the oil, spark plugs etc myself. Fast forward to a month ago and 1500-2000 miles since that service and the CEL has come back on and stayed on.

I got a cheap OBD reader from eBay which is giving me the following fault code:

P0133

o2 sensor circuit

Slow response Bank 1

Sensor 1

From what I have read, this is likely a faulty sensor. Is it the one at the front of the engine which sticks out through the heat shield between the engine and the radiator fan? Looking on eurocarparts, is it called a Lambda sensor? Any particular brand I should or shouldn't go for? Is it easy to remove? It looks like the heat shield has to come off (maybe a problem given how rusty it is)?

I am assuming it is this sensor that is at fault and not something else earlier on in the system? The idle control valve does need replacing it seems. I had it off earlier in the year to clean but I guess it really is dying as that is giving the same problems as before.

Thanks :)

[mjt]

Is it called a Lambda sensor?

Yes, the o2 (oxygen) sensor is also called a Lambda sensor. It measures the amount of oxygen in the exhaust gases and the signal is used by the ECU to adjust the air/fuel ratio. A second one after the catalytic converter allows the ECU to do a comparison to detect if the cat is working efficiently. Sensor 1 will be the one you identified poking through the manifold shield.

[dhr90]

Yes, the o2 (oxygen) sensor is also called a Lambda sensor. It measures the amount of oxygen in the exhaust gases and the signal is used by the ECU to adjust the air/fuel ratio. A second one after the catalytic converter allows the ECU to do a comparison to detect if the cat is working efficiently. Sensor 1 will be the one you identified poking through the manifold shield.

Thanks! So this code is just telling me the sensor needs replacing and not something else?