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Old 02-05-2008, 11:11 PM   #1
Dewback9
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Default Lots of CELs

So I'm fed up with having my CEL and Cruise light constantly flashing at me and I need to find an answer. I have done plenty of searches and read through numerous threads about each of these codes and they all have said different things as being the culprit, so I thought I would start a thread for my issues. Here it goes: I have had a CAI and a catback exhaust on my car for about 6 months now. During those 6 months I had no CELs what so ever. But recently I have decided to go catless with a full header back system and obviously had the CEL and Cruise light on when I first got it done. I first tried the resistor fix on the rear O2 sensor and that did not seem to work at all. Went back to normal and had the code pulled and it was a P0131. Had it erased and drove the car for about a week and the same code reappeared, P0131. So I bought a new front O2 sensor because the old ones threads finally gave out. At the same time I had also put in spark plug anti-foulers for the rear O2 sensor. Put them both in along with the new sensor and had no issues for about 700 miles. Problem solved right? WRONG! I was on my way to the Detroit Autoshow and about 1.5 hours in, HELLO CEL! Had it pulled and here is what it was:


P0171 - Fuel Trim System Lean Bank 1

P0137 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 2

P2096 - Post Catalyst Fuel Trim System Low Limit

P0140 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1Sensor 2

P0171 (the guy said it was on there twice)


So I had them erased and everything was fine. This past weekend I was driving to Chicago and guess who came to visit? Mister CEL was back in town. Haven't had it pulled yet, but my guess is that it is the same friggen codes again. So with my unnecessarily long rant over with anyone have any suggestions as to what could be wrong and what I could possibly do to fix my endless problems besides the obvious response of "don't be catless"? Maybe have it tuned and have the second O2 sensors readings completely blocked or if that is even possible? Let me know what you guys think.
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Last edited by Dewback9; 02-06-2008 at 11:01 AM.
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Old 02-06-2008, 01:37 AM   #2
williaty
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Your rear O2 sensor, or the wiring going to it, is screwed. That explains your 137, 140, and 2096 codes. On the newer ECUs, the rear O2 sensor influences fueling, you get the 171 as well.

You've just pissed around with your exhaust quite a bit. Make sure everything is installed correctly and fastened correctly. Make sure you haven't cut or melted any wires. Make sure you haven't broken the O2 sensor.

Since you're catless, you'll never make the rear O2 sensor happy and, since fueling is affected by it, you HAVE to have it installed. You're probably better off to go to a HFC like the random tech that's known to cause fewer problems and only a 420 when it does. You can then disable the 420 and leave the O2 sensor functioning to make the fueling come out right.
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Old 02-06-2008, 11:09 AM   #3
Dewback9
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Thanks for the reply. The rear O2 seems to be in good working order. The wiring seems perfect, no melting or anything like that has become of it. When I removed it from my original system it came right out, so I don't think it is damaged at all physically. Who knows. Also everything is tightented and fastened correctly so I don't think that is the problem either.

So anyways what you are saying is that it is next to impossible to go catless without tripping some sort of code? I have been thinking about going with a HFC but I just havent been able to justify the price of it and then also having it still have a code on. Another question I had was could I have the ECU tuned and just have the parameters reset for the rear O2 sensor in order for it to not get pissed off at me every other week? I'm not really familiar with tuning yet, so any help in that area would be great.
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Old 02-06-2008, 12:34 PM   #4
drummerRS2505
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Going completely catless and not throwing any CELs is near impossible with the newer finicky subaru ecu's. Yeah I would recommend raising the car up and double checking that all the xhaust stuff is lined up good and fastened correctly and i would check the wiring where you originally had the MIL resistor thing spliced in. I would sodder the wiring and then heatshrink then elect. tape that part to produce the least electrical resistance. Then i would try it without any spacers or anti foulers. I think that using these AF is the cause of the p2096 p2097 codes (I have 2 AF on mine and i get this code every time). Then after all that is good you should only have to deal with the P0420 code and you code wrap the header and paint it (DEI kit) and they may help somewhat but because you are catless obviously you'll still pop a 420 code sometimes.
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Old 02-06-2008, 01:58 PM   #5
williaty
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Quote:
Originally Posted by Dewback9 View Post
Thanks for the reply. The rear O2 seems to be in good working order. The wiring seems perfect, no melting or anything like that has become of it. When I removed it from my original system it came right out, so I don't think it is damaged at all physically. Who knows. Also everything is tightented and fastened correctly so I don't think that is the problem either.
Well, you're not getting the "I don't have a cat and I'm pissed about that" code but you are getting mechanical/electrical failure codes. There's something physical going on here that needs to be fixed. Once you get ride of the codes you have by fixing whatever is causing them, you should have nothing but a 420 left (which is a fact of life with a track pipe).

Quote:
So anyways what you are saying is that it is next to impossible to go catless without tripping some sort of code? I have been thinking about going with a HFC but I just havent been able to justify the price of it and then also having it still have a code on. Another question I had was could I have the ECU tuned and just have the parameters reset for the rear O2 sensor in order for it to not get pissed off at me every other week? I'm not really familiar with tuning yet, so any help in that area would be great.
It's absolutely impossible to go catless without a 420 and it's very unlikely that the 420 will be the only code. With a good HFC like the Random Tech, there's a very good chance you won't have any CELs and if you do, it's going to be the 420 (assuming you fix the other problems) which can be safely disabled in software if your car is supported for flashing.

The parameters for the rear O2 sensor and the conditions for throwing a CEL can't be altered via tuning.
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Old 02-06-2008, 02:58 PM   #6
Dewback9
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Well it looks like I have some work to do this weekend then. I will definately be double checking everything that you two have described to check and recheck again. I'm will be more than happy to live with just a 0420 code than five other ones. I will also be doing some research on a HFC as well.
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Old 02-06-2008, 05:30 PM   #7
LTracer
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Quote:
Originally Posted by williaty View Post

Since you're catless, you'll never make the rear O2 sensor happy and, since fueling is affected by it, you HAVE to have it installed. You're probably better off to go to a HFC like the random tech that's known to cause fewer problems and only a 420 when it does. You can then disable the 420 and leave the O2 sensor functioning to make the fueling come out right.
A catless track pipe with the AF/sensor extended removed should also result in the P0420 if your not bent on getting a HFC. It's possible to eliminate all CEL's with an AF if you play with the spacing distance from the exhaust stream (I've yet to see this but it's theoretically possible for our cars). Too far in the stream = P0420, too far removed = 02096. I opted to just error to the side of P0420 by rewelding the track pipe with a new bung. I'd then recommend adding the MIL fix and deleting the P0420 if it comes up, this should minimize the fuel trim consequences of running catless as much as possible.

DO NOT solder your connections, the recommended method for connecting O2 sensor wires is crimping. Do some searching, this topic has been beaten to death.
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Old 02-07-2008, 08:01 PM   #8
Dewback9
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So I got it scanned again today, and I only got a P2096 and a P0137....Weird. Plan on taking out my spacers and checking my wiring on Saturday to see if that makes any difference. Hopefully I can get rid of the P2096 and only have a P0420 that will come up here or there. Only time will tell if I have solved the problem...
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