lab2370 Posted March 19, 2021 Share Posted March 19, 2021 2009 Legacy, basically stock. It Started with getting a an intermittent P2096 "Post catalyst Trim System Too Lean Bank 1" And could smell it running a little rich Eventually code became consistent and ran very rich. Then it progressed and started throwing these codes P0137 " 02 Sensor Circuit Low Voltage Bank 1 Sensor 2" and P0031 "HO2S Heater Control Circuit Low Bank 1 Sensor 1" And now finally it's to the point where its causing a misfire in cylinder 1.I replaced both the pre and post cat 02 Sensors which didn't seem to help. So anybody got any ideas on what to check next? Link to comment Share on other sites More sharing options...
Jveerz Posted March 19, 2021 Share Posted March 19, 2021 2009 Legacy, basically stock. It Started with getting a an intermittent P2096 "Post catalyst Trim System Too Lean Bank 1" And could smell it running a little rich Eventually code became consistent and ran very rich. Then it progressed and started throwing these codes P0137 " 02 Sensor Circuit Low Voltage Bank 1 Sensor 2" and P0031 "HO2S Heater Control Circuit Low Bank 1 Sensor 1" And now finally it's to the point where its causing a misfire in cylinder 1.I replaced both the pre and post cat 02 Sensors which didn't seem to help. So anybody got any ideas on what to check next? Did you replace the sensors with OEM replacements? just asking because I had a similar issue when replacing my front O2 with one from Rockauto, replaced it with an oem on and my issue was gone. Link to comment Share on other sites More sharing options...
lab2370 Posted March 22, 2021 Author Share Posted March 22, 2021 Thinking it was an AC delco sensor Link to comment Share on other sites More sharing options...
apexi Posted March 22, 2021 Share Posted March 22, 2021 Maybe an exhaust leak somewhere? "My 2005 Legacy gt threw the same codes last year, which lead to a lot of trial and error fixes as well. My mechanic then found a small hair-line crack in the my downpipe right at the flange. Your vehicle isn't quite as old as mine, and I also see you live in florida. So maybe rust/wear and tear on the bottom of your car isn't as common as up here in Canada, but I suppose it's worth checking for" https://www.subaruforester.org/threads/persistant-cel-codes.638625/post-6459306 Link to comment Share on other sites More sharing options...
lab2370 Posted March 22, 2021 Author Share Posted March 22, 2021 Maybe an exhaust leak somewhere? "My 2005 Legacy gt threw the same codes last year, which lead to a lot of trial and error fixes as well. My mechanic then found a small hair-line crack in the my downpipe right at the flange. Your vehicle isn't quite as old as mine, and I also see you live in florida. So maybe rust/wear and tear on the bottom of your car isn't as common as up here in Canada, but I suppose it's worth checking for" https://www.subaruforester.org/threads/persistant-cel-codes.638625/post-6459306 It's actually an Oregon care and definitely a little rust in spots. I guess maybe a tiny exhaust leak is possible, definitely dont hear any major leak. If it were an exhaust leak then it would like to be pretty far up the exhaust correct? Close to the engine if it's causing problems before it even hits the first 02 sensor? Link to comment Share on other sites More sharing options...
apexi Posted March 22, 2021 Share Posted March 22, 2021 It's actually an Oregon care and definitely a little rust in spots. I guess maybe a tiny exhaust leak is possible, definitely dont hear any major leak. If it were an exhaust leak then it would like to be pretty far up the exhaust correct? Close to the engine if it's causing problems before it even hits the first 02 sensor? This is a little over my head, but I think you're right that it probably wouldn't be too far from the sensors. I'd start near there and check everywhere, and maybe look for black soot or something where the gaskets are, leaky gasket Link to comment Share on other sites More sharing options...
JmP6889928 Posted March 22, 2021 Share Posted March 22, 2021 Wet your hands and feel around every joint with the car running. If there is a leak, you'll find it. My thinking is you have clogged converters to make it run so rich. Link to comment Share on other sites More sharing options...
lab2370 Posted March 23, 2021 Author Share Posted March 23, 2021 Wet your hands and feel around every joint with the car running. If there is a leak, you'll find it. My thinking is you have clogged converters to make it run so rich. Hmm I'll have to try that. As for the Cat, I bought the car used (only 2k!)and it was already running rich but the guy had had the Cat done about 40k miles ago complete with paper work. So it SHOULD be good, doesn't mean it is though. Link to comment Share on other sites More sharing options...
boxkita Posted March 23, 2021 Share Posted March 23, 2021 is it an oem cat? Build my car Boxkita Track days Link to comment Share on other sites More sharing options...
lab2370 Posted March 23, 2021 Author Share Posted March 23, 2021 is it an oem cat? The paperwork for when it had it worked on was from a Subaru dealership so I'd assume it's OEM Link to comment Share on other sites More sharing options...
Jlaumann Posted March 23, 2021 Share Posted March 23, 2021 I am actually having the exact same issue with my Legacy. Its a stock 2006 Legacy, 2.5l. Kicking codes p0137 & p2096. I have changed the spark plugs, and wires, mass air flow sensor, and the downstream O2 sensor. I put about 250 miles on it, and then the check engine light came on again. I am not sure what else to do at this point. Link to comment Share on other sites More sharing options...
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