7 replies to this topic

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Morning lads,

 

 

Car details: 2003 Forester XS, Standard EJ25 NA engine.

 

 

I have been getting shit fuel economy in the Foz lately. It only took 330km's to get to the fuel light this week!!

I have my suspicions that it's the oxygen sensor, but there is no check engine light on or anything.

 

In my first Liberty which had the same engine, the fuel economy dropped like the Foz but there was a check engine light saying that the oxygen sensor was buggered.

 

 

 

 

My question is, can the oxygen sensor be buggered without showing a CEL?

Is it worth replacing it anyway?

 

 

Cheers,

Tom.

 

 

 

(P.S. according to the workshop manual there's 2 oxygen sensors, is there a way to tell which one is playing up?)

[Robbks]

yep,
usually the rear o2 will fail and just give a constant voltage reading to the ECU that is within it's limits. So it doesn;t throw a CEL.

it will usually have a stored code in the ECU for "O2 slow performance" or something like that

Find your local Auto Service Solutions store www.efi.com.au and get a plug in Bosch sensor with the correct length wiring.
you may need to back the pins out of the plug and swap with your original plug. but no soldering/ joining needed

I got one last week for my Gen3 Libby, EJ25. same problem. Under 300km from a tank. (40L) not good

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Cheers Rob.

 

So it's usually the rear one that goes? Are the front and rear sensors the same? (I can only find 1 type on eBay, that's where I got it from for the last car and it worked a treat, but that only had one sensor)

 

How much did you pay for the sensor?

 

Cheers.

[Robbks]

Forget ebay.

http://au.bosch-auto...-shop.com/en/43

Yep the rear is the one that's the culprit for fuel economy (until you get to later models)
Usually just a normal 3-wire, narrowband sensor.
I paid about $125

My MY03 Libby only has the one, I'm unsure about the Forester, it was around a changeover period from having one or both.

Best to eyeball under the car., mine only has the one in the front of the cat-converter (Y-Pipe where the headers join the rest of the exhaust)

[Cam.]

The front o2 sensor is responsible for bad economy.

The rear o2 sensor is only responsible for making sure that catalytic converter is doing it's job.

[Delete This Account]

The front o2 sensor is responsible for bad economy.

The rear o2 sensor is only responsible for making sure that catalytic converter is doing it's job.

Cheers Cam.

 

I thought the front one would usually be the first to go too, because it gets the full force of the emissions before the cat. 

[bobbyjimmy]

Front sensor is A/F (air fuel).

Rear sensor is O2.

[Robbks]

While the above IS true, if the car has two sensors.
You need to confirm if your model has one or two sensors.