O2 Sensor Woes

[Subaru_Nation555]

When I installed my TBE a couple of weeks ago, I had to extend the wiring for the oxygen sensor to reach the bung on the downpipe. So the other I was driving on the highway and the check engine light comes on. I pull over and check the code-its for the O2 sensor. So I start the car up again and the light was off so I kept driving. Long story short it only throws the code for the O2 sensor when driving at highway speeds for a couple of minutes. Am I correct when saying that the ECU throws the code where it gets an incorrect voltage reading from the sensor? So could it be a faulty sensor or might I need to redo the wiring job. Any thoughts? Thanks.

[J-MoNeY]

I'd check the wiring job again and make sure that no gunk from the install got on the O2 sensor.

[vrg3]

It's possible that the wiring isn't actually working at all. With the sensor disconnected, you pretty much only get the CEL when cruising on the highway sometimes.

Are you confident in your wire extension? The wires on the sensor side of the connector are made of some kind of alloy that's very hard to electrically join.

You can check the signal from the sensor with a voltmeter attached to the oxygen sensor signal pin of the ECU. Or you can use my scantool if you have access to a PC-compatible laptop with a printer port.