dj.snodgrass Posted March 16, 2013 Share Posted March 16, 2013 Hello Fellow owners! Newbie to the forum. I am hoping someone has seen this error as well and has some answers as to its origin. I am seeing this on a 2008 Legacy 2.5i base with zero mods and we are the second owners so maintenance prior to us is unknown. I have performed many searches online and come up with nothing. Some time ago, Let's say 6 months, my wife was on her way home. She was climbing a hill which she does everyday on her way home. Due to its slope she down shifted into fourth at which time the car had no power and came to a stop where she pulled off. When I arrived the car would not start. It turned over just fine but no go. I plugged in my handy code reader to see if there were any codes listed or pending - none. Then I notice that there is a code showing on the odometer (until this point, i didn't even know this was a thing). It read "er AA". Now I called my local indy who was a tech at the local subby dealer for 18 years or so who did not know and had not seen that error before. After calling the dealer, same answer. I have the car towed to the dealer who says: "I reset the computers and I was able to drive around the parking lot. I think you need a new BIU (Body interface Unit) and also new keys as they need to be paired properly. Also don't use your little code reader. I messes with the computer and we are unable to read everything properly". I think yeah right, the car has OBD then I should have no problem, that's just you trying to get me in here for everything. Now I called bull on the computer and keys thinking there must be someway to reprogram keys. Anyhow, I left it at that and carried-on. Until recently, no more issues. While on a long trip through that wicked eastern seaboard snow storm/blizzard the CEL illuminates and I pull the code - something with the Evap system so I clear the code and tighten the gas cap. Seems to have fixed that one. Prior to this, I notice that the car seems to be missing and the engine "bucks" periodically. I decided that at 200000 KM's maybe the plugs had never been changed so I did just that with NGK plugs. Missing seems to have been fixed. I did notice that the plugs were very badly overused and the electrodes were pretty much non-existent. Soon after, the CEL illuminates again and I read it. P0420, catalyst system efficiency below threshold. Crap! Bring it to my indy who says its likely the Cat that is bad. So based on the time he spent looking I figure he does a quick connector and wire check and says must be the cat. After doing some research I am thinking of trying the rear O2 sensor. And now this week, I plug in my code reader to clear the CEL P0420 and I notice something odd. When I plug in my reader, my engine temp gauge flinches and then goes to normal, then the er AA returned. Scared the car might not start again I leave it running and go straight home where I park in the garage. I shut it off and voila, no start. I tried once or twice more and it started with no error in the odometer again. So, I have gone through all of this in case any of this leads to an answer on the weird error. Based on the only two other odometer codes I have seen - er IU and er SS - and their simplicity IU being the BIU and SS being a Speed Sensor the only thing I can come up with is Air Assist. Would a faulty Air Assist Solenoid cause any of these symptoms, like a no start condition or a possible weird Air/Fuel mix causing the P0420? Sorry for the winded post but I thought I would fill everyone in as complete as possible on what I have seen lately. Thanks for any replies! Link to comment Share on other sites More sharing options...
CashSeeAO Posted May 13, 2014 Share Posted May 13, 2014 Hi, I am wondering if you were able to resolve the issue(s) with the "Er AA" and P0420 codes. Any update is greatly appreciated. Link to comment Share on other sites More sharing options...
Max Capacity Posted May 13, 2014 Share Posted May 13, 2014 FWIW, the p0420 code is a bad front O2 sensor. if you have this, replace the front O2 sensor with a OEM one, My aftermarket one lasted 2 years. They don't last forever. I doubt we'll ever hear back from the OP, he only has 2 post... 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
CashSeeAO Posted May 13, 2014 Share Posted May 13, 2014 Thank you for your response. Noted on only using OEM front O2 sensor. Link to comment Share on other sites More sharing options...
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