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Old 02-18-2021, 05:27 PM   #1
WRXXXED
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Default Multiple codes, don't know what else to do...

Okay so in December 2020 I pulled the engine to do a clutch. Since then every so often I have gotten the same 3 repeated codes even after replacing sensors.

P0139 (rear o2 sensor slow response)
P0457 (gas cap/evac leak)
P0852 (park/neutral position switch)

I have since replaced the o2 sensor but it still shows up? What else other than a bad sensor would cause it? I haven't even messed with the neutral switch so could it have just simply gone bad? I don't have any left over vacuum lines after reinstalling the engine so possibly I didn't get one on all the way?
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Old 02-18-2021, 07:06 PM   #2
Elbert Bass
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Since the wiring for the rear O2 and the neutral switch are in the same harness that runs down the left side of the transmission I would look there first - unplugged connector, stretch/broken/pinched wires...
Be aware those neutral switches are prone to failure as well.

The P0457 could be you didn't reconnect the evap vent hoses at engine, broke the evap solenoid, have a failed evap vent solenoid. It could also be not related to the work you did. If you didn't leave something loose then a smoke test would be in order.
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Old 02-18-2021, 07:46 PM   #3
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Quote:
Originally Posted by Elbert Bass View Post
Since the wiring for the rear O2 and the neutral switch are in the same harness that runs down the left side of the transmission I would look there first - unplugged connector, stretch/broken/pinched wires...
Be aware those neutral switches are prone to failure as well.

The P0457 could be you didn't reconnect the evap vent hoses at engine, broke the evap solenoid, have a failed evap vent solenoid. It could also be not related to the work you did. If you didn't leave something loose then a smoke test would be in order.
Oh, that sounds like a great place to start. I did have trouble getting the engine and trans separated until I realized I forgot to take the clutch fork shaft out. I did jack up the trans so much it started to lift the car off the jack stands so it probably pinched that harness. Thank you ill take a look at that and check some vacuum diagrams to see if I missed anything
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Old 02-20-2021, 02:04 PM   #4
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Okay so took that sub-harness out, cut the shielding and sure enough, 3 wires were cut, the dark and light green and the black wire, got them back together, put some heat shrink around them and the codes went away. Also found that my TiAL BOV line had come off so I got that back on there to fix the vaccum leak.

Thank you Elbert Bass for pointing me in the right direction!
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Old 02-20-2021, 03:02 PM   #5
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Quote:
Originally Posted by WRXXXED View Post
Okay so took that sub-harness out, cut the shielding and sure enough, 3 wires were cut, the dark and light green and the black wire, got them back together, put some heat shrink around them and the codes went away. Also found that my TiAL BOV line had come off so I got that back on there to fix the vaccum leak.

Thank you Elbert Bass for pointing me in the right direction!
That P0457 may come back since that is an evap code related to the fuel tank plumbing. It may take a while before the evap test runs again, especially if you are where the temp doesn't get above 50 degrees.
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Old 02-27-2021, 09:04 PM   #6
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Alright so just in case anyone is having the same issues, since fixing the trans sub-harness wiring the neutral switch code went away and my slow response oxygen sensor (O2 sensor) was still popping up. Took a look at the plugs and my cyl 1 plus porcelain was cracked and I was using the wrong heat range for the boost I was running!

I switched from a SILFR6A plug to a LFR7Aix plug and gapped it down to .025" and since then the car hasn't thrown any codes since.
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Old 03-02-2021, 10:24 AM   #7
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P0139 popped up again... found another thread that was saying the rain caused it most of the time but I don't think thats the case for me. Im not sure what else to do at this point, it all started after I replaced the clutch but my o2 sensor harness didn't appear pinched and all the wires for that were in tact, just the neutral switch harness was cut, they weren't on the same harness either (2010 sti) they were separate so I'm going to just replace the sensor one more time and not use a $38 rockauto special and try a Bosch sensor.. wish me luck
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Old 03-03-2021, 07:59 AM   #8
Elbert Bass
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Quote:
Originally Posted by WRXXXED View Post
P0139 popped up again... found another thread that was saying the rain caused it most of the time but I don't think thats the case for me. Im not sure what else to do at this point, it all started after I replaced the clutch but my o2 sensor harness didn't appear pinched and all the wires for that were in tact, just the neutral switch harness was cut, they weren't on the same harness either (2010 sti) they were separate so I'm going to just replace the sensor one more time and not use a $38 rockauto special and try a Bosch sensor.. wish me luck
Could be cheap sensor - I recommend using Denso, they make the OEM and it's plug-n-play. Usually much cheaper at RockAuto.

Another thing could be a leak at the gasket between downpipe/midpipe. A leak will let air in and make the O2 sensor "see" diluted air. That code indicates the O2 sensor is not tracking closely with what the A/F sensor is reading and an air leak is one thing that will cause it.
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Old 03-14-2021, 01:48 PM   #9
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Quote:
Originally Posted by Elbert Bass View Post
Could be cheap sensor - I recommend using Denso, they make the OEM and it's plug-n-play. Usually much cheaper at RockAuto.

Another thing could be a leak at the gasket between downpipe/midpipe. A leak will let air in and make the O2 sensor "see" diluted air. That code indicates the O2 sensor is not tracking closely with what the A/F sensor is reading and an air leak is one thing that will cause it.
Okay so I took a look at the potential leak and there wasn't any space in between the down and mid pipes, the gasket was in tact when I took it apart but replaced it anyways. So I'm going to take a guess and say that the sensor is just being weird because its not OEM. Replacing it with a Denso is my last resort, after this I will have no idea what to do

Last edited by WRXXXED; 03-14-2021 at 02:53 PM.
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Old 03-20-2021, 07:57 AM   #10
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Quote:
Originally Posted by WRXXXED View Post
Okay so I took a look at the potential leak and there wasn't any space in between the down and mid pipes, the gasket was in tact when I took it apart but replaced it anyways. So I'm going to take a guess and say that the sensor is just being weird because its not OEM. Replacing it with a Denso is my last resort, after this I will have no idea what to do
Popped up again and taking it to a local shop Thursday for a diagnosis
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Old 03-20-2021, 12:36 PM   #11
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I suggest you check the power going to the heater of the sensor to make sure that is good. If the power is low it would take longer to get the sensor up to proper operating temperature.
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Old 03-26-2021, 08:09 AM   #12
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Took it to a shop yesterday and they told me there was a hole in the downpipe. They welded it and said its all good now. Im still not convinced thats the problem because I took the downpipe off to inspect it and I see where they welded. It was a gouge in the pipe from when I was driving to Allentown, PA to get my project car injectors flow tested and cleaned and hit a massive pothole. It rotated the downpipe towards the axle and was rubbing there... I did end up having to replace the axle but there wasn't a leak in the downpipe, hell I never got a check engine code for a slow oxygen sensor until this past fall. Im convinced that itll pop up again... ill keep you all posted
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Old 03-27-2021, 03:36 PM   #13
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Quote:
Originally Posted by WRXXXED View Post
Took it to a shop yesterday and they told me there was a hole in the downpipe. They welded it and said its all good now. Im still not convinced thats the problem because I took the downpipe off to inspect it and I see where they welded. It was a gouge in the pipe from when I was driving to Allentown, PA to get my project car injectors flow tested and cleaned and hit a massive pothole. It rotated the downpipe towards the axle and was rubbing there... I did end up having to replace the axle but there wasn't a leak in the downpipe, hell I never got a check engine code for a slow oxygen sensor until this past fall. Im convinced that itll pop up again... ill keep you all posted
Sure enough, it popped up again... when my dad had his integra built he was asked to he wanted them to disable some of the codes that will pop up if they don't. Is that an option using the access port?
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Old 03-28-2021, 10:19 AM   #14
Elbert Bass
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Quote:
Originally Posted by WRXXXED View Post
Sure enough, it popped up again... when my dad had his integra built he was asked to he wanted them to disable some of the codes that will pop up if they don't. Is that an option using the access port?
Sounds like you need to take it back to the shop - they misdiagnosed the issue and performed a repair that didn't resolve your issue.
In mechanic speak "they are now married to it"

BTW: you don't by chance have one of those O2 fitting spacer on that rear O2 sensor? That can make your sensor read "slow".

Last edited by Elbert Bass; 03-28-2021 at 10:24 AM. Reason: add BTW
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Old 03-29-2021, 09:28 AM   #15
WRXXXED
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Quote:
Originally Posted by Elbert Bass View Post
Sounds like you need to take it back to the shop - they misdiagnosed the issue and performed a repair that didn't resolve your issue.
In mechanic speak "they are now married to it"

BTW: you don't by chance have one of those O2 fitting spacer on that rear O2 sensor? That can make your sensor read "slow".
Yeah, ill be calling them to tell them and they should take another look at it at no cost since it didn't fix my issue.

As for the BTW, I do not have a spacer in-between the o2 sensor and bung.
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Old 04-11-2021, 08:34 AM   #16
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So it's been a couple weeks but when they re-diagnosed it they found a crack in the header at the flange of my KillerB holy header. Now they do have a lifetime warranty but unfortunately thats only for original buyers and I bought the car with the header on it, they also said that there is a leak at the V-band between the header and uppipe so I guess I'll try a new clamp but I don't think that'll fix the leak. Going to try a couple of things with that v-band mating and report back but ill be welding that flange crack and see how it goes
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Old 04-22-2021, 01:49 PM   #17
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Quote:
Originally Posted by Cougar4 View Post
I suggest you check the power going to the heater of the sensor to make sure that is good. If the power is low it would take longer to get the sensor up to proper operating temperature.
What should the proper voltage level be? 5v I assume? How can I check that? I have a voltmeter do I just check the power and ground together?
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