Lambda / Oxygen Sensors On A 2004 Fiesta (Help Please :) )

[JNY12]

Hi there,

Hopefully some of you smart people will be able to help me...

I have an engine warning light on and got it diagnosed with the following code...

"P0030 H02S Heater Control Circuit Bank 1 Sensor"

I understand this is the lambda sensor that needs replaced but I don't know if its the upstream or downstream sensor from the CAT. How would I know which one needs replaced other than try both when replacing? Also, is there a difference in sensor between front / back sensors i.e. could I buy the wrong one? Looks like they are both 4-pin.

Thanks in advance :)

[stef123]

This doesn't necessarily mean the sensor is at fault, it could be an electrical issue elsewhere.

The code is referring to bank 1 sensor 1 so it will be the precat sensor.

Be vary of cheap aftermarket universal sensors, they are usually rubbish.

[Stoney871]

I concurr, bank 1 is the front sensor.

[stef123]

I think that bank 1 refers to 'header' 1, where in a v6 there is 2 headers if that makes sense?

It's sensor 1 or sensor 2 you need to worry about.

[JNY12]

Thanks for advice guys. Anyone got any recommendations for sites to buy from - I'm from Glasgow and have bought from EuroCarParts before and they seemed ok (not sure how pricey they are in comparison though). And are both pre/post CAT sensors the same part? Thanks

[stef123]

Thanks for advice guys. Anyone got any recommendations for sites to buy from - I'm from Glasgow and have bought from EuroCarParts before and they seemed ok (not sure how pricey they are in comparison though). And are both pre/post CAT sensors the same part? Thanks

ECP are generally ok, some of the stuff they sell is quite poor though so just be aware of what brands you are buying.

NGK, Bosch or Denso stuff should be of good OE quality.

the sensors may well be the same although i wouldnt have thought the rear one would be heated - the front one is heated as it will only work when above a certain temp, the quicker it gets there the more efficient the engine will be. i suspect the electrical connectors will be different though

[Andy 1965]

I got my Lambda sensor from Partco behind the Kelvin Hall last year. It was an NGK and cost £57. No issues with it.