Engine management light come up on my drive home last night, I've narrowed it down to the upstream oxygen sensor but i am struggling to find a replacement online. Any suggestions on where i could find the correct one?

The car is a 2012 1.0 99ps Ford Focus

More info: My OBD2 scan tool gave the code P0420 - Catalyst system efficiency below threshold (Bank 1)

eBay have plenty. Search 1771995

How have you come to the conclusion the upstream sensor is faulty and not the catalyst? Bear in mind it's a broadband sensor . 

2 minutes ago, iantt said:

eBay have plenty. Search 1771995

How have you come to the conclusion the upstream sensor is faulty and not the catalyst? Bear in mind it's a broadband sensor . 

Thanks for the reply! I plugged in my cheapo OBD2 reader and only sensor 2 was showing any voltage, sensor 1 didn't register anything even after a 30 minute drive. Does that sound like the issue or am i way off?

Wideband O2 Sensors do not work in the same way as the old narrowband ones, and a generic OBD reader is unlikely to be of any use because the wideband sensors do not produce any voltage.

If you get yourself set up with FORScan you should be able to monitor the current, which should stay around 0, and also the heater circuit for the sensor. Better still, if you go into Mode 6 tests, there should be useful info in there for both sensors, although what info there is in Mode 6 varies from car to car.

2 minutes ago, Tizer said:

Wideband O2 Sensors do not work in the same way as the old narrowband ones, and a generic OBD reader is unlikely to be of any use because the wideband sensors do not produce any voltage.

If you get yourself set up with FORScan you should be able to monitor the current, which should stay around 0, and also the heater circuit for the sensor. Better still, if you go into Mode 6 tests, there should be useful info in there for both sensors, although what info there is in Mode 6 varies from car to car.

Is the 02 sensor after the cat also wideband? as i get a reading from that one. Ill have a look at forscan thanks for the reply.

2 minutes ago, noscail said:

Is the 02 sensor after the cat also wideband?

No, the downstream one will not be a wideband one as far as I know. 

8 minutes ago, Tizer said:

No, the downstream one will not be a wideband one as far as I know. 

Ahh okay cheers mate.

 

Does the after cat sensor appear to be working correctly in this screenshot, this was taken while idling.

That screenshot just shows that it is switching, that doesn't mean it is working correctly.

I've just thought on.. I've been using Shell V Power in the car for the past 2 months, but used some cheaper Texaco fuel the morning it happened. Could that cause it to throw a check engine light? 

 

I've since cleared the code and drove about 50 miles without it reappearing.