O2 sensor Check engine light... - VW Forum :: Volkswagen Forum
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post #1 of 22 (permalink) Old 03-07-2010, 04:28 AM Thread Starter
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O2 sensor Check engine light...

So I had a check engine light from not having a cat (according to the previous owner) so I installed a 42dd o2 sensor spacer and cleared the existing code

The code was P0420 which is Catalyst System Efficiency Below Threshold (Bank 1) So I went ahead and cleared it, a day or so later the CEL came back and I ran the reader again (I dont have a vag-com and I am just using a normal reader) and it came up with 2 new codes

P0138 - O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)

and

P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)

So I am guessing I need to replace the rear o2 sensor? I can just get one of the Bosch ones right? I just unscrew the sensor, unplug it from the box (which is located near the rear o2 sensor right?) and plug it back in and erase the code?

I dont think I need to adjust the spacer at all because the spacer is about as far as it can get...I was only able to screw it on half a turn (which was tough in itself) and it is pretty snug on the pipe. It is also oriented so that the o2 sensor faces the rear of the car.
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post #2 of 22 (permalink) Old 03-07-2010, 09:54 AM
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Don't get the Bosch ones they sell at AutoZone or w/e, get an OEM one from the dealer because the Bosch ones tend to burn up a lot quicker. Bank 1 is the pre-cat 02 sensor

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post #3 of 22 (permalink) Old 03-07-2010, 10:51 AM
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i feel your pain. i have to tweek mine to get just right. im going to be installing a high flow cat. soon so it should help. i just keep clearing mine, comes back after a few miles of driving. i think mine is being thrown due to the o2 sensor being on the bottom, thus letting build up get onto it. i just have to spin the test pipe.

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post #4 of 22 (permalink) Old 03-07-2010, 10:53 AM
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Fubar do you have APR flash?

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post #5 of 22 (permalink) Old 03-07-2010, 04:19 PM Thread Starter
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What about the "sensor 2" part? Do I need the front one then? Or perhaps both? If I ignore this...will there be problems? Im guessing running too rich/lean?
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post #6 of 22 (permalink) Old 03-07-2010, 07:33 PM
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im running unitronic stage 2. i would just replace 1 o2 sensor first. it might be possible that you have it spaceed out too far and it is barely getting a reading.
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post #7 of 22 (permalink) Old 03-07-2010, 08:40 PM
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Quote:
Originally Posted by fubardub View Post
im running unitronic stage 2. i would just replace 1 o2 sensor first. it might be possible that you have it spaceed out too far and it is barely getting a reading.
I was gonna say that if you have APR you can get a reflash for 30 bucks or something that completely and permanently eliminates the pre-cat and/or post-cat 02 sensor code.

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post #8 of 22 (permalink) Old 03-07-2010, 09:12 PM Thread Starter
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Quote:
Originally Posted by fubardub View Post
im running unitronic stage 2. i would just replace 1 o2 sensor first. it might be possible that you have it spaceed out too far and it is barely getting a reading.
Which one do I replace then the pre or post cat? Would having it too far actually give a code because I really cannot adjust it any further...the spacer only screws into my pipe a half turn and I cannot turn it anymore than that :/

Would it be cheaper to just go to a shop and have the o2 sensors replaced as opposed to buying the sensors ($130 for the rear one for example) and replacing them myself? I'm assuming they would use bosch sensors. How much quicker do they burn up compared to the oem ones?
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post #9 of 22 (permalink) Old 03-07-2010, 10:49 PM
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Assuming I am understanding this correctly you are throwing a CEL because of the o2 censor. I don't know if it would be the same code as one that would show if you didn't have a catalytic converter installed. Anyway I have unitronic stage 2 reflash and they told me that the car will never throw a CEL for a catalytic converter or lack of. They said if it ever does I could bring it to them and they will fix it. I am putting on a new exhaust this month so I don't know yet so I will find out after I remove my cat if it throws a CEL. If I read correctly you also have unitronics. You should talk to the place that did it for you.

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post #10 of 22 (permalink) Old 03-07-2010, 11:36 PM Thread Starter
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Is this directed to me? I have the neuspeed flash
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post #11 of 22 (permalink) Old 03-08-2010, 01:24 PM
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my bad, fubardub has uni.

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post #12 of 22 (permalink) Old 03-21-2010, 07:28 PM Thread Starter
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ok so yeah, I replaced sensor 2, and adjusted my spacer (got it to be a little closer) and its been fine for almost a week...but the same codes came back today

Is it sensor 1 that needs to be replaced now?
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post #13 of 22 (permalink) Old 03-23-2010, 03:31 PM Thread Starter
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anyone?
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post #14 of 22 (permalink) Old 03-23-2010, 10:11 PM
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Do you need it to pass emissions?

Cody

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post #15 of 22 (permalink) Old 03-24-2010, 12:34 AM Thread Starter
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Nah, I dont have a cat so I went to a guy who would write me off.

Honestly, if it isnt causing my car to run poorly, I really could care less...I really just dont want the CEL left on; if I leave it on, I wont know when I have other problems
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