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OK 600 miles codeless after P0420 mechanical fix (anti-fouler) and today I got two P2096 codes (second one reads P2096P) and some at nasioc report this being related to 05 (with O2 cheaters in place). http://forums.nasioc.com/forums/show....php?t=1131438

I did install a biggyback antifouler but will take the advice to remove and drill it and use on driver's side cat and probably get another one and use on the third rear sensor behind where the dual exhaust joins.

Has anyone dealt with the 05 before? I will post back or edit but I read somewhere that it has something to do with how the 05 reads the difference between the sensors that varies from other years. Just my luck...

Any thoughts?

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Hmmm...

That probably means the after cat sensors also adjust fuel trim and are not solely for checking efficiency of the cats. You might actually have to fix this one the "right" way. :eek:

 

The P at the end of the second one probably means it's a "Pending" code. Which according to Innova means:

A code recorded on the "first trip" for a "two-trip" code. If the fault that caused the code to be set is not detected on the second trip, the code is automatically erased.

 

 

Try unhooking the battery - for a half hour to reset the ECU and see if it comes back.

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The cat destroys sensor data - sensors after the cat cannot be used for tuning.

 

GD

@GD, that's my understanding as well. The 05 has two upstream sensors (one on each down pipe) and three post cat sensors (downstream) one after each cat and one after the two exhaust join and sits atop a "muffler" (God help me if it's another cat back there)

Setup looks something like top exhaust here

@Fairfax I used a cheapo code reader to erase the codes. Fingers crossed but I hate the uncertainty.

Edited by brus brother

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My computer is getting ready to go on a ski trip through the back yard via window pane airlines. :mad:

It locked 3 times trying to open the 05 FSM I have.

Anyway...

This is Subaru's definition for this code...

DTC P2096 POST CATALYST FUEL TRIM SYSTEM TOO LEAN BANK 1

DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

 

That was about all I got to read before the computer locked up. It just doesn't like acrobat anymore I guess. I think it's about time to wipe this thing out and start over.

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I think they are refering to some function that attempts to prevents damage to the cat's by reading the exhaust gas immediately after them and then also farther downstream...... That's what it sounds like anyhow.

 

GD

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I think they are refering to some function that attempts to prevents damage to the cat's by reading the exhaust gas immediately after them and then also farther downstream...... That's what it sounds like anyhow.

 

GD

@GD I hope this would indicate that modding the other two downtream sensors will prevent a recurrence??

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Just curious. With 24" of snow on the ground, I haven't proceeded any further with mods but after erasing the codes, my code reader still says that MIL not ready for cats and evap. Does this change to ready after a few drive cycles (what is a drive cycle?? distance... speed...)

I'm afraid that this won't pass inspection as is...

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The definition of a drive cycle varies. For some systems it is just time with the key on. Others needs a whole string of conditions to be met in a certain order before the monitor will be set as "ready".

 

95 and 96 Subarus have exceptions for emissions testing because several of the monitors reset after each key cycle, which means they will never be "ready" during testing. After that Subaru fixed the issue, so all models 97 and after have to have monitors set "ready" to pass testing.

 

IIRC the Evap system has the most difficult monitor as far as completing the proper drive cycle in order to get it to set "ready".

 

Just keep driving. You may need to make several trips of various duration from 5 to 30 minutes to get it to set.

 

 

I haven't had the chance to look into the deal with the O2 sensors. Though I'm not entirely sure I could find anything useful. :-p

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Took it for a 55 mph drive for about 20 minutes. All sensors except egr are ready. Found this:

http://www.ultimatesubaru.org/forum/showthread.php?t=99980

How's that for complicated??

UPDATE: Wife had it out for a couple of hwy. runs (she probably stays closer to 55 mph than Mr. Leadfoot) and now all sensors scan ready! Yippee.

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P2096 back. "Post catalyst fuel trim system too lean (Bank 1)"

History:

Trying to solve P0420, I first tried one antifouler drilled out and piggybacked to one not drilled out and that gave me P2096.

Then I eliminated the piggybacked one but that returned the P0420 even though the sensor was "out of the stream" so I next tried two drilled out antifoulers thinking it would be "out of the stream" but still getting enough input to show it as working.

Help me noodle this. There are 2 upstream sensors (one on either downpipe), 2 downstream sensors (one behind either cat) and one additional downstream sensor atop the rear cat after the two pipes join.

Is it relevant that I am only modding the bank one sensor behind the first cat? Is the code simply relevant to the difference in readings between the front (on the engine downpipe) and that first rear sensor (behind the passenger cat) or is that rear sensor thrown into the mix and warranting attention?

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Found the following quote:

"Post catalyst fuel trim system too lean (Bank 1)"

apparently

"it looks like its only happening on 05MY models... as i read somewhere the rear o2 sensor actually has pulsating ohm resistance, and not a steady one.."

http://forums.nasioc.com/forums/showthread.php?t=1699259

Would this explain why the cheater anti-fouler throws a P2096 code on the 05MY but is working fine for other years?

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Can your scanner monitor/record live data?

 

I'm wondering if you just have a bad sensor. That might have caused the P0420 code as well. Did you test/replace any sensors in attempt to remedy the p0420 code?

What I can find says basically the same as causes for P0420. The ECU isn't seeing the change in voltage that it wants to see from the sensor. In this case the voltage is staying too far in the lean direction. Perhaps finding a happy medium with the size of the hole drilled in the anti fouler will fix the problem.

Have you tried drilled as well as un-drilled by themselves?

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Can your scanner monitor/record live data?

 

I'm wondering if you just have a bad sensor. That might have caused the P0420 code as well. Did you test/replace any sensors in attempt to remedy the p0420 code?

What I can find says basically the same as causes for P0420. The ECU isn't seeing the change in voltage that it wants to see from the sensor. In this case the voltage is staying too far in the lean direction. Perhaps finding a happy medium with the size of the hole drilled in the anti fouler will fix the problem.

Have you tried drilled as well as un-drilled by themselves?

@Fairtax

Post #12 in this thread lists the various combinations of threaded and non-threaded anti-foulers that I have tried. I think I covered all the bases as far as the first downstream sensor in bank 1.

 

The car seems to run well which is why I started monkeying around at the downstream sensor which only appears to be related to emissions. I also thought the culprit to be the first downstream sensor behind passenger (bank 1) cat and not the sensor atop the rear (3rd) cat after the two pipes join because it did specify bank 1 in the code P0420.

I can eliminate code P0420 by modifying the first downstream bank 1 sensor with two antifoulers (either with two drilled or one drilled and one undrilled) but that is when the P2096 appears. One drilled antifouler didn't work at all.

 

I suppose I could swap the pair of up- and down-stream sensors side to side and see if the codes changed from bank 1 to 2...? It's just so darn cold here now with 10 degrees and the remnants of a 24" snowfall.

 

Mine is a simple code reader and not a data-logger. I may have to bite the bullet and ask the dealer to do a diagnostic run to see what's going on before I start replacing cats.

Do you see any holes in my reasoning?

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Mine is a simple code reader and not a data-logger. I may have to bite the bullet and ask the dealer to do a diagnostic run to see what's going on before I start replacing cats.

Do you see any holes in my reasoning?

When any conventional fix creates other problems, it's usually best to start back at square one.

Before going to see a dealer see if any friends or friends of friends have access to a better scanner, or even better an Oscilloscope, so you can check out the sensor outputs.

Swapping sensors side to side is a good idea.

 

How many miles are on this car?

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When any conventional fix creates other problems, it's usually best to start back at square one.

Before going to see a dealer see if any friends or friends of friends have access to a better scanner, or even better an Oscilloscope, so you can check out the sensor outputs.

Swapping sensors side to side is a good idea.

 

How many miles are on this car?

Yeah I'm back at square one. Removed all cheater anti-foulers and cleared codes. Waiting for drive cycles to set all sensors to ready which will then likely throw the p0420 code. I am having the dealer do the timing belts this week and will ask the tech to go for a drive with a laptop setup with datalogger to see what's up.

I keep seeing the OBDII to USB cables and software on eBay for $20 but I don't have the know how to read the output anyway.

There seems to be some complications with MY 05

Found the following quote:

"Post catalyst fuel trim system too lean (Bank 1)"

apparently

"it looks like its only happening on 05MY models... as i read somewhere the rear o2 sensor actually has pulsating ohm resistance, and not a steady one.."

http://forums.nasioc.com/forums/show....php?t=1699259

Edited by brus brother

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Sorry to revive such an old thread. Did you ever find a solution to this problem on your 05? I have a 2005 Legacy 2.5i that is doing the exact same thing. It seems to run fine which makes me think the cats are fine, but I received the p0420 code, tried to do the mechanical fix, and ended up with e p2096. Please let me know what your final solution was.

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Sorry to revive such an old thread. Did you ever find a solution to this problem on your 05? I have a 2005 Legacy 2.5i that is doing the exact same thing. It seems to run fine which makes me think the cats are fine, but I received the p0420 code, tried to do the mechanical fix, and ended up with e p2096. Please let me know what your final solution was.

Welcome to the board TJ. Unfortunately I still get the code 0420. I haven't replaced the cat $$. I bought a code reader/clearer Link

It will also test that all systems are "ready" as in ready for emissions testing!

I clear the code and it stays off for a while.

The code comes and goes and I only need be concerned in passing emissions every two years. Clear the code, drive a fews cycles and all systems will test ready. Drive to test center, smile, pay the fee and away you go.

Edited by brus brother

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Thanks for the response. I've been thinking about living with the code also, but it really drives me crazy when the cruise control doesn't work. I think I might replace the cat as soon as it warms up in Minnesota. I'll let you know if it fixes my problem.

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Thanks for the response. I've been thinking about living with the code also, but it really drives me crazy when the cruise control doesn't work. I think I might replace the cat as soon as it warms up in Minnesota. I'll let you know if it fixes my problem.

I don't really use cruise control so I see your point. Keep us posted.

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