Hi all,

 

We have been getting an intermittent check engine light and finally was able to get the code read.

 

H02S Heater Control Circuit ( Bank 1, Sensor 1)

 

I have seen some of the previous posts on this but am wondering were the sensor is to make the checks? 

 

This on our 04 outback, 2.5 with around 160K  miles on it.

 

Thank you,

I'm a little confused.

 

In your title, you said P0300 which is for a random/multiple misfire.

Then you mention an O2 sensor circuit code. Which is a different code then P0300.

 

Which code do you have?

If you got a heater circuit code at 160k, then you need a new upstream O2 sensor. 

 

If you got a P0300 that's a horse of a different color and there are many causes - start with NGK plugs and wires and go from there.

 

GD

That is my mistake the code is 

 

P0030

 

So where would I look for the upstream O2 sensor?

 

Don,

Front catalytic.