Downstream (post cat) O2 sensor replacement help

[arslan]

Okay so i got a Bosch O2 sensor. Screwed her into the cat (required fenangling) then all of a sudden the plug didn't fit with the harness. Great! I notice there is another harness that comes with the bosch plug but how the hell do I know which wire goes wear? I went ahead and shoved the O2 sensor into the harness anyways but now I am getting a heater core code for that sensor. Has anyone run into this issue where the plug wasn't an exact fit for the harness? Let me know! Thanks for the help.

[fR3ZNO]

We're gonna need some more info than that. Do you have info like the part number? I've used Bosch O2 sensors before that are direct fit and never had this issue. Did you get a universal fit sensor or something?

[arslan]

Hmmm... Yeah it was supposed to be a direct fit Bosch. It is not a universal. I am guessing o'reilly autoparts sold me the wrong one. I will follow up later today. You would think they could sell me the right one.

[arslan]

Okay so this is the one I have for my 02 audi a4 1.8t

https://www.ecstuning.com/b-bosch-pa...ach/16978~bos/

It is definitely not a direct fit and others have reported the same thing on their b6's as well from the reviews I was reading. The directions to swap the harnesses out are just terrible.

[All_Euro]

[frogspit]

I used bosch 1k0998262 / 0258006978 / 16978 and it plugged right in to my 02 AMB. Got it on amazon for $70

https://www.amazon.com/dp/B00NT9QC38..._oJzKBbE9WDYY0

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[arslan]

Thats the one I have. Not a direct fit. You have to rewire the housing harness with the one that harness located in the image above but it has vague directions.

[arslan]

I used bosch 1k0998262 / 0258006978 / 16978 and it plugged right in to my 02 AMB. Got it on amazon for $70

https://www.amazon.com/dp/B00NT9QC38..._oJzKBbE9WDYY0

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I am talking about the downstream (post Cat) O2 sensor. This has the upstream (pre cat) bosch number on it and it also has the post cat. This is deceiving because if you look at ECS there are two different types.

[frogspit]

I wonder if this one already has the correct wire harness.

I bought it from the seller B2C auto parts and it plugged right in to my downstream connector no harness or connecter modifications needed


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[seanf86]

you can run a dremel down the side of the o2 sensor connector and put a groove into it in the same spot as the sensor you removed so it fits in the factory connector, I did that as I didnt feel like trying to get the pins out. Been well over a year now, no issues, lots of times Bosch does this so they only have to make one sensor that fits a wider range of cars.

[frogspit]

I used this one for upstream

https://www.amazon.com/dp/B00427MIFC..._nMAKBbR1ENQD5

other one i posted for the downstream

they both fit mine perfectly right out of the box


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[arslan]

you can run a dremel down the side of the o2 sensor connector and put a groove into it in the same spot as the sensor you removed so it fits in the factory connector, I did that as I didnt feel like trying to get the pins out. Been well over a year now, no issues, lots of times Bosch does this so they only have to make one sensor that fits a wider range of cars.

Yeah I just shoved the plug in the harness and it was able to connect but I am still throwing a code. I will post back in an hour with the actual code I am getting but it was something about O2 heater core issue. Could it be a dead O2 sensor? Because I just connected the O2 sensor on their half assed, it got me thinking the wiring was different on the harness vs the O2 sensor side.

[arslan]

I used this one for upstream

https://www.amazon.com/dp/B00427MIFC..._nMAKBbR1ENQD5

other one i posted for the downstream

they both fit mine perfectly right out of the box


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Yeah I replaced the upstream and everything was smooth. Not so much for the downstream.

[arslan]

The codes in the red are the culprits I am getting. I confirmed with AutoZone and they said I got the correct sensors for the downstream. It just isn't a direct fit to the wiring harness. You guys think the plug may be dead?Screenshot_20180906-171858.jpeg

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[seanf86]

unplug it and measure the resistance with a multimeter between the 2 pins with the white wires going to them. I can't for the life of me remember what its going to say but itll be something, if the heaters bad you won't get any resistance.

[arslan]

unplug it and measure the resistance with a multimeter between the 2 pins with the white wires going to them. I can't for the life of me remember what its going to say but itll be something, if the heaters bad you won't get any resistance.

Multimeter ordered. O'Reilly said they will replace it if needed.

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[arslan]

Not getting any resistance between the two white wires. Just 0L is showing up on the screen. These are the only codes I am getting now. Could bank one sensor 2 refer to the upstream O2 sensor?Screenshot_20180908-145451.jpeg

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[seanf86]

sensor 2 is post cat, sounds like you've got a bad heater.

[arslan]

Of course the hardest one to replace is the faulty one.

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[arslan]

That fixed it. Somehow I smashed the O2 sensor when I first installed it. New one is working great

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[danielg4]

I bought it from the seller B2C auto parts and it plugged right in to my downstream connector no harness or connecter modifications needed


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This means that you must have already had the harness connector replaced, because I just got off the phone with B2C Auto Parts myself, and they told me the sensor with that ASIN will not fit my 03 AMB. I got their number off their Amazon profile after reading this thread.

Edit: I've since spoken to a shop, and sensors with a connector that fits simply don't exist anymore. The recommended solution is to remove the protruding plastic on the car's connector that fit into the groove on the old sensor's connector.