dfalk Posted March 21, 2016 Share Posted March 21, 2016 I have an 05 Legacy 2.5i with just under 80K miles on it. I bought the car years ago with 40K on in and around 50K or so the CEL came on and indicated a bad front O2 sensor. I replaced it (not sure what brand) and it worked just fine for 25K miles or so. Last year in May, around 75K, the CEL came on once again for bad O2 sensor. I bough a new one, this one was a Bosch 1593, put it in and it worked just fine but not for long. This weekend CEL came on once again and just a couple hundred miles below 80K. My CEL codes are P0031 and P2097. So this one last 5K miles and not even a year. Could this last one maybe just have been a bad one from the factory or is there something else going on in my car that could cause these to go bad so quickly? I'm going to replace it again, should I try a different brand, I think Denso is the other one that's available. Any help is appreciated. Link to comment Share on other sites More sharing options...
JmP6889928 Posted March 21, 2016 Share Posted March 21, 2016 The design of the OE exhaust manifold (unequal length) puts a substantially increased amount of heat on the front O2 sensor. If you are on stock tune, it's tendency is lean anyway which generates even hotter temperatures. Go with an OE and they do last longest but still don't have a great life span. Link to comment Share on other sites More sharing options...
dfalk Posted March 21, 2016 Author Share Posted March 21, 2016 Go with an OE and they do last longest but still don't have a great life span. Do you know what brand is OE? Link to comment Share on other sites More sharing options...
gimpydingo Posted March 21, 2016 Share Posted March 21, 2016 Denso/Bosch Have you done any logging on this car? Since JmP is stating a lean condition adds heat, wondering if you have a leak somewhere that is adding to the failure rate. Link to comment Share on other sites More sharing options...
CapnJack Posted March 22, 2016 Share Posted March 22, 2016 Denso/Bosch Have you done any logging on this car? Since JmP is stating a lean condition adds heat, wondering if you have a leak somewhere that is adding to the failure rate. Turbo inlet would be the first place I would look. They tear and can cause a lean condition. Have you performed a learning view to see what your fuel trims are at? Link to comment Share on other sites More sharing options...
dfalk Posted March 22, 2016 Author Share Posted March 22, 2016 Have you done any logging on this car? Umm, I don't know what that is! Turbo inlet would be the first place I would look. They tear and can cause a lean condition. Have you performed a learning view to see what your fuel trims are at? Also have no idea what that is! This is a non trubo engine though. Link to comment Share on other sites More sharing options...
CapnJack Posted March 22, 2016 Share Posted March 22, 2016 Umm, I don't know what that is! Also have no idea what that is! This is a non trubo engine though. Sorry - Missed that it was a 2.5i. I'd still check the intake piping after the MAF for any vacuum leaks. Make sure all the hoses are on an intact. Link to comment Share on other sites More sharing options...
dfalk Posted March 25, 2016 Author Share Posted March 25, 2016 Sorry - Missed that it was a 2.5i. I'd still check the intake piping after the MAF for any vacuum leaks. Make sure all the hoses are on an intact. No prob. I replaced the O2 sensor tonight and checked everything I could under the hood. Everything looked fine as far as I could see. I disconnected the battery while replacing the sensor, the check engine light went off, so I'll report back after I've drove 50 miles or so to see what happens. Link to comment Share on other sites More sharing options...
covertrussian Posted March 25, 2016 Share Posted March 25, 2016 OEM is Uses Denso. If you don't want to throw away extra money for Subaru branded one get Denso 234-9120. Subaru buys these and just puts a subaru sticker on the box and charges $60 more. 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
pop-pop Posted March 25, 2016 Share Posted March 25, 2016 Bit late… but I also had multiple O2 sensors (and CCs) go bad starting at around 60k, but there is an extended warranty on emissions system parts and Subaru covered the cost. Maybe this is location-dependent, cant recall. I am in California. Link to comment Share on other sites More sharing options...
gimpydingo Posted March 25, 2016 Share Posted March 25, 2016 Bit late… but I also had multiple O2 sensors (and CCs) go bad starting at around 60k, but there is an extended warranty on emissions system parts and Subaru covered the cost. Maybe this is location-dependent, cant recall. I am in California. Interesting. I had one go at like 60k as well. New one has been fine @ 90k now. Link to comment Share on other sites More sharing options...
dfalk Posted March 29, 2016 Author Share Posted March 29, 2016 OEM is Uses Denso. If you don't want to throw away extra money for Subaru branded one get Denso 234-9120. Subaru buys these and just puts a subaru sticker on the box and charges $60 more. You sure that's the right part number? I bought a Denso 234-9122 Since I've installed it I've drove 50 miles and the CEL hasn't came on. Before it was coming on within 25 miles of resetting the CEL light. Link to comment Share on other sites More sharing options...
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