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Subaru OBD-II Questions
This page will list all the Check Engine Light questions and answers asked of us pertaining to Subaru vehicles. Subaru models include the Impreza, WRX, Forester, Outback, Tribeca, Legacy, and more.
Question: OK I have a 2005 Subaru Impreza 2.5 RS 76,000 miles No more warranty. I have aftermarket borla headers on it and different muffler. It was fine for 2 months now I keep getting a P0131 CEL so i replaced the front O2 sensor and it has not fixed the problem I still get the code. Funny thing is when I turn car off and turn back on its gone and comes back within 2 mins. when I'm idling or on the gas its goes to closed loop then when decelerating it goes back to open loop and back fires some not loud but a gargle sound then throws the P0131 CEL and stays open. also on acceleration and idle its hesitant and jerky through the RPMs and at idle rpms jump between 900 and 500 rpm looking for a fix I was told to try and wrap the headers but it doesnt sound like its what would fix it..thank you for your time - Noah, September 2008
Answer: Hi Noah. A P0131 is described as 02 Sensor Circuit Low Voltage (Bank I Sensor I). The first thing that comes to mind is where is the front O2 sensor now in relation to where it was prior to the header swap. If it's further down the pipe then it's possible the exhaust gases are cooling down a bit more than before. That's why I think someone suggested you wrap your header, that will help hold that heat in and possibly improve the exhaust gas temperature (EGT) readings at that O2 sensor. So sure, go ahead and wrap the header, it's not going to hurt anything. It should also slightly lower the under-hood temperature as well.
The P0131 code refers to the O2 sensor circuit, so I'd also recommend you inspect the wiring & connectors leading to the O2 sensor. One other note - cheap quality (non-OEM) oxygen sensors are more likely to fail sooner than OEM ones. So if you're still having problems, use an oscilliscope & DVOM to see if the sensor is working right, if you have to replace it again, get a genuine Subaru part. I found a good article on P0131, so check it out too.
Question: I have a 1999 Subaru Impreza Outback Sport with 101,500 miles. The check engine light is on with a P0325 code. What should I do about this? I just had brakes replaced and 90K maintenance done. The car seems to be running smoothly. - Connie, August 2008
Answer: Hi Connie, thanks for contacting us. A friend of mine has a 1999 Subaru Forester. I scanned the codes and he had a P0325 code as well. The code definition is Knock Sensor Circuit Malfunction. You can read more info on the code here [P0325]. Basically what that code means is there's a problem with the knock sensor, the electrical connector, or the wiring. On my friend's car they replaced the knock sensor and that resolved the problem. Good luck!
Question: I have an 2005 Subaru WRX STI 45k miles 2.5L I get a code P0245 Turbo wastegate solenoid low I was wondering what might cause this. - Manuel, August 2008
Answer: Hi Manuel, thanks for the question. I've gotta ask, do you have any warranty left? If so, let the dealer take care of this issue. If not, I'd recommend you check out the operation of the wastegate solenoid. I don't have any specific instructions but definitely verify it's operation. I suspect it's probably sticking at times or it could be an electrical issue. You'll probably want to buy a Subaru WRX repair manual or borrow one from the public library. Find out what wires are what, where the solenoid is located, etc. Go from there. Verify all wiring & connectors leading to the solenoid. Try applying voltage directly to the solenoid to see if it's working correctly or not. I suppose you could also just replace it, depending on the cost.
If in doubt as to your ability to perform the above, please contact a trusted, qualified technician.