O2 Sensor for Subaru EJ20

[IanMills]

I am after a we bit of advice,
I fitted a EJ20 engine into my van about four years ago using mostly RJES stuff including the loom. Its been running like a dream until recently and an error code appeared. it indicated the O2 Sensor. This was replaced with a brand new unit order from top quality supplier. I did not buy a cheap replacement from e-bay.
Fitted the sensor and the engine run fine for about 5 minutes, its running like a bag of spanners and the same error code for the O2 has come up with no other error code.
a) how do I test the sensor to make sure its faulty or not
b) how do I test the wing to make sure there is not a fault within the wiring causing this.
c) just buy another O2 sensor
Thanks for any help
Ian

[Aidan]

Ian my experience is scooby ecu doesn't mind a cheap lambda, unlike MV wbx,

have you tried a power off ecu reset and relearn ? or have you done that and not driven it yet, if so it will probably overidle and be unhappy till it's done a full temp cycle or twlo on road and been restarted

to test you need to get at the signal wire from the lambda with a test probe and check the volts cycling, I drilled a 2.5mm hole in the side of the connector block so I could do it once I'd figured out which was which, then I proved the faulty one was staying low, and then after fitting replacement could observe it cyling normally and after clearing code from ecu it was fine for a year till I broke the car and sold the manifold to a local scooby owner with the lambda in, have fitted same cheap one to the new exhaiust on the engine now in pick up and exhaust is clean

[Domino]

Put a Voltmeter on the signal wire which is blue on the sensor side of the connector , should be varying between 0.5 to 0.9 volts

[IanMills]

Thanks for the replies. I did do an ecu reset before starting the engine with the new O2 sensor. Started it up and went for a run that's when it started to cough and splutter after about 10 minutes.
Will check readings and see what I get.
Many Thanks