P0420 - Replaced Cat and 02 sesnor, this thing won't go away.

[phyregold]

Long story short, I had a 2.2 and got swapped with with a 2.5.  I replaced the cat because it was legitimate snapped in half and I also replaced the 02 sensor, all together I am about 1200$ in the repair of exhaust and sensor and I'm pushing the car's value.

 

My question is, with the swap of the 2.5 could I be having other issues?   Since I've replaced the cat and o2 sensor, is there only things I should take a look at?  There are no other codes on the car but I do remember reading about a mass air slow sensor?  I took it to a good shop and they said there doesn't appear to be an electrical issue.  Any advice would be great!

[1 Lucky Texan]

exhaust system leak?

a:f problem?

[nvu]

did you go from nonturbo to turbo?  the p0420 is pretty tricky to catch even on the original car.  even throwing on a different exhaust system could trigger it.  don't try and chase the problem itself, but get other things dialed in and worry about p0420 last.  the car will run fine with p0420 code and no other codes, at least anything before 2007.  it just won't pass smog.

with that, some things to check if you haven't done so already:

your mass air flow sensor is probably okay.  make sure the car runs strong in closed loop, no misfires or rough idling.  part throttle should be smooth, put it in 1st and see if it can creep along smoothly in idle.  creep along smoothly 1000-1500rpm. try 2nd gear  if it's bucking or missing, then check your maf sensor, intake, vacuum leaks...

on the exhaust side of things, make sure the entire path from engine to the rear cat has no leaks.  the flex joint and gaskets just before and after the cat are usual suspects.  test with whatever way you think will help, i don't know of any surefire way

for me, i had one car that would pop a p0420 every couple months, even did pressure smoke testing and never found the anything.  only by chance one year i decided to sand a rusty looking flange only to find that it was slightly bent, the other mating flange was bent in the same direction so everything mated up and sealed fine, but was C shaped ever so slightly, you can't even tell by eye.  after getting everything flat again, the problem went away for good.  still on original cat from 2002

[idosubaru]

On 9/26/2023 at 2:22 PM, phyregold said:

Long story short, I had a 2.2 and got swapped with with a 2.5.  I replaced the cat because it was legitimate snapped in half and I also replaced the 02 sensor, all together I am about 1200$ in the repair of exhaust and sensor and I'm pushing the car's value.

 

My question is, with the swap of the 2.5 could I be having other issues?   Since I've replaced the cat and o2 sensor, is there only things I should take a look at?  There are no other codes on the car but I do remember reading about a mass air slow sensor?  I took it to a good shop and they said there doesn't appear to be an electrical issue.  Any advice would be great!

 

No this is not due to the compatibility of the two engines.  You're fine to swap 00-03 EJ's engines and ECU's all day long without issue.  To reply to your private message - no I don't know any shops in your city.

Two very easy solutions:

1. Remove the REAR oxygen sensor, install a spacer, then reinstall the oxygen sensor: 

Here's the spacers:  https://www.ebay.com/itm/402784625218?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160811114145%26meid%3D316d681a7a3b4c1885d614c9c25790d0%26pid%3D100667%26rk%3D1%26rkt%3D8%26sd%3D402784625218%26itm%3D402784625218%26pmt%3D1%26noa%3D1%26pg%3D2351460%26brand%3DDorman%2FHelp&_trksid=p2351460.c100667.m2042

Typically drill out the center and you can double stack the two of them together, but I've installed them without drilling though I'm not sure it was the same part I linked here.  I've just bought them and installed them but I bought a bag of them many many years ago and they might be a slightly different part. 

2.  I've seen other versions in the past, have never used one, not sure if it's overkill, but here's a slick attempt: 

https://www.fastwrx.com/products/oxygen-sensor-spacer-with-cat

 

If you want to attack a repair of the current configuration:

1. There can be ZERO leaks - Check all manifold and flange mating surfaces for any leaks.
2.  Are there any other codes?
3. Assuming the swap was done correctly this is absolutely not an engine compatibility issue. 
4. For clarity you should remind us what year is the A. Engine  B. Intake manifold wiring  C. ECU
5. The installed converter is used or new aftermarket low grade which frequently still throw P0420 codes.

 

[phyregold]

On 9/28/2023 at 5:54 PM, idosubaru said:

 

No this is not due to the compatibility of the two engines.  You're fine to swap 00-03 EJ's engines and ECU's all day long without issue.  To reply to your private message - no I don't know any shops in your city.

Two very easy solutions:

1. Remove the REAR oxygen sensor, install a spacer, then reinstall the oxygen sensor: 

Here's the spacers:  https://www.ebay.com/itm/402784625218?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160811114145%26meid%3D316d681a7a3b4c1885d614c9c25790d0%26pid%3D100667%26rk%3D1%26rkt%3D8%26sd%3D402784625218%26itm%3D402784625218%26pmt%3D1%26noa%3D1%26pg%3D2351460%26brand%3DDorman%2FHelp&_trksid=p2351460.c100667.m2042

Typically drill out the center and you can double stack the two of them together, but I've installed them without drilling though I'm not sure it was the same part I linked here.  I've just bought them and installed them but I bought a bag of them many many years ago and they might be a slightly different part. 

2.  I've seen other versions in the past, have never used one, not sure if it's overkill, but here's a slick attempt: 

https://www.fastwrx.com/products/oxygen-sensor-spacer-with-cat

 

If you want to attack a repair of the current configuration:

1. There can be ZERO leaks - Check all manifold and flange mating surfaces for any leaks.
2.  Are there any other codes?
3. Assuming the swap was done correctly this is absolutely not an engine compatibility issue. 
4. For clarity you should remind us what year is the A. Engine  B. Intake manifold wiring  C. ECU
5. The installed converter is used or new aftermarket low grade which frequently still throw P0420 codes.

 

 

Thanks, here is a question about the spacers, do you stack both together or just 1?  I have tried this route and now have driven over 300 miles with every stop and go, idle, and coast and heat on and heat off and cold start and 1/4 gas tank and I cannot get the O2 ready to be ready.

 

Thanks!

Edited October 3, 2023 by phyregold

[wtdash]

Everyone else on here must be psychic, What year and model you working on?

 

 

[idosubaru]

On 10/3/2023 at 4:02 PM, phyregold said:

 

Thanks, here is a question about the spacers, do you stack both together or just 1?  I have tried this route and now have driven over 300 miles with every stop and go, idle, and coast and heat on and heat off and cold start and 1/4 gas tank and I cannot get the O2 ready to be ready.

 

Thanks!

I don't know because I bought a bag years ago that are one length so I don't stack them, but they're longer than the typical packs of two. I would install one, then install 2 if that doesn't work. 

But it should work *IF the rest of the exhaust doesn't have leaks.

What does "I cannot get the 02 ready to be ready" mean?  Is the check engine light still on?  Is the P0420 still on? 

Or are you talking about the monitors that need populated after a reset? 

It's not a 1996 vehicle or ECU right?  I thought you were talking about 01-02 vehicle/engines. 

1 hour ago, wtdash said:

Everyone else on here must be psychic, What year and model you working on?

You've been here long enough you should be psychic by now, the Matrix must have a glitch. 

He started another topic recently and private messaged me, so I've been following a long a tiny bit.

[brus brother]

Phyregold's proffile:

Location

Delaware

• Vehicles
  Outback 01

   

  So my fortune teller's guess is his car may be a Studebaker (turbo)

[phyregold]

On 10/4/2023 at 4:26 PM, idosubaru said:

I don't know because I bought a bag years ago that are one length so I don't stack them, but they're longer than the typical packs of two. I would install one, then install 2 if that doesn't work. 

But it should work *IF the rest of the exhaust doesn't have leaks.

What does "I cannot get the 02 ready to be ready" mean?  Is the check engine light still on?  Is the P0420 still on? 

Or are you talking about the monitors that need populated after a reset? 

It's not a 1996 vehicle or ECU right?  I thought you were talking about 01-02 vehicle/engines. 

You've been here long enough you should be psychic by now, the Matrix must have a glitch. 

He started another topic recently and private messaged me, so I've been following a long a tiny bit.

 

Sorry for the ambiguity.

The check engine light is not on and when I go to inspection the monitors are not ready (O2 and Evap), The vehicle is not a 96, the vehicle is an 01 which originally had the 2.2 now now a 2.5, I also have no idea what the 2.5 came out of.

I've now driven over 800 miles and done everything in the list below, and several other sites/forums suggestions.  I'm starting to wonder if the spacer is causing the monitors to not be ready.

 

https://www.suoutback.com/drive_cycle-1102.html

 

 

23 hours ago, brus brother said:

Phyregold's proffile:

Location

Delaware

• Vehicles
  Outback 01

   

  So my fortune teller's guess is his car may be a Studebaker (turbo)

LOL, not a Studebaker, but also not a turbo, N/A, Impreza

Edited October 5, 2023 by phyregold

[Daskuppler]

This code for me was bad head gaskets and I was burning coolant.

[phyregold]

Okay, so the check engine light finally came on, and this time I don't have a P0420 at all I have a P0440.  I took it to autozone and their print out says check the gas cap, well I legitimately don't have a gas cap so I put one one.

 

So I guess my questions are, one do I not have to worry about the P0420 anymore?  I don't know if the sensor is ready until I go to inspection on Tuesday.

 

I also, bought a gas cap and put it on, do I have to reset the code and wait? Or will it clear itself because it thinks it's fixed?   Also, I've never had a P0440 code until now, would the space cause it? 

 

Thanks!

Edited October 7, 2023 by phyregold

[idosubaru]

Spacer doesn’t cause P0440…or any codes.  It also doesn’t cause any monitor issues  

96s are legally exempt from the monitors not populating because they never do.  but most emissions techs don’t know  I thought yours was an 01 ish but wanted to check  

The code will reset itself as soon as the issue is corrected, or after a few miles. 

some national chain stores will read the codes for free.  Call and ask if the local ones to you do and if they can see the monitors so you can check before you go. 

[phyregold]

8 hours ago, idosubaru said:

Spacer doesn’t cause P0440…or any codes.  It also doesn’t cause any monitor issues  

96s are legally exempt from the monitors not populating because they never do.  but most emissions techs don’t know  I thought yours was an 01 ish but wanted to check  

The code will reset itself as soon as the issue is corrected, or after a few miles. 

some national chain stores will read the codes for free.  Call and ask if the local ones to you do and if they can see the monitors so you can check before you go. 

Thanks!  I know when I reset the code for the P0420 it took about a week for this check engine light to come on, hopefully it will go away... hopefully..

 

If not, guess I am troubleshooting P0440...

[brus brother]

You didn't have a gas cap?? building a Molotov cocktail container?

OK well, it should reset itself but if you have a code reader, you can check to see if there are any "readiness" issues.

Don't reset the codes for now.
I wouldn't let Autozone etc or you to reset the code because then you might have to wait for the proper # and type of drive cycles for all the readiness monitors to reset.

[phyregold]

21 hours ago, brus brother said:

You didn't have a gas cap?? building a Molotov cocktail container?

OK well, it should reset itself but if you have a code reader, you can check to see if there are any "readiness" issues.

Don't reset the codes for now.
I wouldn't let Autozone etc or you to reset the code because then you might have to wait for the proper # and type of drive cycles for all the readiness monitors to reset.

I'm priobably going to start a new P0440 thread, the gas cap didn't do it.  I'm going to wait for Tuesday to verify that the P0420 wen't away when I take it to DMV to see if the monitors are ready.

[brus brother]

get a cheap $20 code reader/eraser like THIS

know before you go to DMV

[idosubaru]

On 10/8/2023 at 9:43 AM, phyregold said:

I'm priobably going to start a new P0440 thread, the gas cap didn't do it.  I'm going to wait for Tuesday to verify that the P0420 wen't away when I take it to DMV to see if the monitors are ready.

It's always some part related to or around the big black box under the rear passengers side corner - look up behind the rear bumper and rear passengers side corner.  There's a big box.  The hoses, nipples, and solenoids are prone to rust and crack due to exposure to salt, snow, rain, dirt, getting hit by rocks, etc.  Pull the box out and see what's cracked/broken or replace the solenoid.  

Here's a diagram of all the hoses and parts.  

https://parts.subaru.com/a/Subaru_2002_Outback-Limited-Wagon/49249678__6025446/FUEL-PIPING/B12-420-05.html

 

[1 Lucky Texan]

^^^ what he said - plus, the filler neck behind the plastic shield gets rusted-out holes.

[phyregold]

On 10/10/2023 at 3:04 PM, idosubaru said:

It's always some part related to or around the big black box under the rear passengers side corner - look up behind the rear bumper and rear passengers side corner.  There's a big box.  The hoses, nipples, and solenoids are prone to rust and crack due to exposure to salt, snow, rain, dirt, getting hit by rocks, etc.  Pull the box out and see what's cracked/broken or replace the solenoid.  

Here's a diagram of all the hoses and parts.  

https://parts.subaru.com/a/Subaru_2002_Outback-Limited-Wagon/49249678__6025446/FUEL-PIPING/B12-420-05.html

 

 

I truly appreciate everything, I'll be able to hop under the car this weekend.  Quick question, your link is for a 02 outback limited wagon.  I have an 01 Subaru Impreza outback, does the same diagram work?

 

Also, At this point I've now driven 1300 miles, have the po440 code and the monitor is still not ready for the 02, all i can think or is either the O2 sensor is fried or the spacer isn't reading correctly where it'll become available.  I'm going to get the part you have above and replace it, but I can't think after this long something isn't right.

 

So I got a tool and yeah the 02 is still not ready and it shows the 1 code.  It's almost like nothing is getting to the O2 sensor.

 

Is there a way to smoke test or easy way to test this?  Nothing looks out of the ordinary other than it's old and it seems like a lot to just replace it all.

Edited October 13, 2023 by phyregold
more info

[el_freddo]

Smoke testing an O2 sensor won’t show anything. Smoke testing an intake manifold will show up any vacuum leaks. 

How old is your O2 sensor? And did you check the wiring for continuity? 

If your O2 sensor is old it could be dead, or if the signal or heater wiring is damaged it may be offline, either way it should be getting up to temp even in extremely cold weather - this should bring it online (once up to temp). With that said I’d rule out the heater wire and focus on the sensor being dead or a damaged sensor wire. 

What’s the quality of the O2 sensor you used to replace the old one? And is it pinned correctly? Sometimes the pinouts can change and I’ve seen units where you have to correctly pin the plug for your model of vehicle. 

Cheers 

Bennie

[phyregold]

18 hours ago, el_freddo said:

Smoke testing an O2 sensor won’t show anything. Smoke testing an intake manifold will show up any vacuum leaks. 

How old is your O2 sensor? And did you check the wiring for continuity? 

If your O2 sensor is old it could be dead, or if the signal or heater wiring is damaged it may be offline, either way it should be getting up to temp even in extremely cold weather - this should bring it online (once up to temp). With that said I’d rule out the heater wire and focus on the sensor being dead or a damaged sensor wire. 

What’s the quality of the O2 sensor you used to replace the old one? And is it pinned correctly? Sometimes the pinouts can change and I’ve seen units where you have to correctly pin the plug for your model of vehicle. 

Cheers 

Bennie

Hey, sorry for the confusion.  There are two issues currently ongoing.  One is the 02 system won't come ready an the other is the P0440 which I wanted to smoke they the car to find the leak.

 

To answer your question, the 02 sensor is about 7 weeks old, bought brand new from Autozone, and quality I believe is only one they carry?

[1 Lucky Texan]

Denso or OEM (same?) is preferred for sensors. Folks sometimes report problems with aftermarket including Bosch.

[phyregold]

10 minutes ago, 1 Lucky Texan said:

Denso or OEM (same?) is preferred for sensors. Folks sometimes report problems with aftermarket including Bosch.

I honestly don't know, I'd have to go and look.  I was originally getting a P0420 which is why I got the exhaust work and the O2 sensor put on.  When I put the new O2 sensor of the P0420 came back so I tried the spacer route.  The problem now is since I put the spacer on the 02 sensor won't come ready (6  tanks of gas 1300 miles later in both highway and city).

 

Part of me wonders if I should take the spacer off, let the p0420 come back, put the spacer back on and see if it goes away.

 

I also never had a p0440 until the spacer, but that could just be a coincidence. 

[brus brother]

My 2005 OB with 2.5 was not compatible with the spacer trick. 2005 MY forward can't be spacer tricked. Since you don't know what MY your 2.5 engine originated from it couldn't hurt to retrace your steps.

Everything I tried, putting a resistor in line etc. just kicked off more codes.

If you can get rid of the 0440 then I'd say just get a code reader and trick the system long enough to pass inspections every 2 years. I did that for 8 years on my 05 before it wore out and was junked. I'm at the same point with my 08 now.

Consider the new exhaust etc as a write off. You might even reinstall the original O2 sensor if you aren't confident of the Autozone aftermarket.

None of the above steps cost more than your time and a few skinned knuckles.

Edited October 15, 2023 by brus brother

[phyregold]

3 hours ago, brus brother said:

My 2005 OB with 2.5 was not compatible with the spacer trick. 2005 MY forward can't be spacer tricked. Since you don't know what MY your 2.5 engine originated from it couldn't hurt to retrace your steps.

Everything I tried, putting a resistor in line etc. just kicked off more codes.

If you can get rid of the 0440 then I'd say just get a code reader and trick the system long enough to pass inspections every 2 years. I did that for 8 years on my 05 before it wore out and was junked. I'm at the same point with my 08 now.

Consider the new exhaust etc as a write off. You might even reinstall the original O2 sensor if you aren't confident of the Autozone aftermarket.

None of the above steps cost more than your time and a few skinned knuckles.

 

How do you trick the system if the 02 won't come ready?  Or are you suggesting putting the 02 back the way it was resetting everything and moving forward?