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?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. 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: Warning lights came on, and I received code P0442 and the gas cap appears to be broken

A P0442 fault indicates a leak in the evaporative emissions system, or EVAP system for short. You are already on the correct path by checking the gas cap first. This is the most common reason for this fault, though it...

Q: (Subaru Forster 2011) AT OIL TEMP is flashing after driving the car for a certain time. smell can be smiled from the gearbox maybe

Was the filter changed as well? If the filter is blocked, hydraulic pressure may not be sufficient to keep the clutches from slipping. That slippage, if it is occurring, causes lots of excess heat. Other possibilities are faulty solenoids and...

Q: Fuel pump won't prime.

Hi there. When you turn the key to begin the starting process, more than 20 individual fuel and ignition system components that must all work together in order to start the vehicle. Due to this fact, the best way start...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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.