Skip the auto shop - Our mechanics make house calls

Q: Computer reads an issue with the oxygen sensor on a Subaru Forester 1999 2.0 Turbo. What is the problem?

asked by on

computer reports oxygen sensor after diagnosis what is the problem

My car has 97000 miles.
My car has an automatic transmission.

Your 1999 Subaru Forester has pre and post catalytic converter oxygen sensors. The pre-converter sensor optimizes fuel trim while the post converter sensor monitors the efficiency of the catalytic converter. A failing pre-converter sensor will degrade vehicle MPG performance. Although a code may set that "identifies" one of these sensors that does not always mean the sensor is "bad". For example, the post converter sensor may show up in a Diagnostic Trouble Code but the real issue is an actually failed catalytic converter. Similarly, a variety of causes, such as sulfur contaminants from leaking valve stem oil seals, and even a failed fuel injector, can cause the pre-converter sensor to fail. Although you could replace the sensor, it will fail as well unless the underlying malfunction is addressed. For a comprehensive diagnosis of the trouble code, and repair, of this issue feel free to contact YourMechanic for assistance.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  • Home
  • Questions
  • Computer reads an issue with the oxygen sensor on a Subaru Forester 1999 2.0 Turbo. What is the problem?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Temperature gauge is fluctuating, sometimes showing overheating.

Hey there. There are combustion gas analyzers that you can buy and use on a DIY basis for this, but I would have a professional perform the diagnostic, and hopefully find the fault elsewhere (other than head gasket leak). You'll...

Q: Jerking when accelerating (after slowing down).

Hi there. From my experience with this vehicle the issue is almost always a failure in the throttle body. It is very common for the throttle body to have an intermittent failure and for it to run like this. Most...

Q: I have An 04 Subaru Outback and my sidelights on my headlights and my running tailight won't turn off with the ignition off. This

Hi there. This issue could be caused by multiple electrical gremlins, ranging from an exposed wire that is creating a short to damage from the ignition relay. The only way to really know for sure or to recommend a repair...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.