Whats different between the 1-3 and 4-6 O2 sensors?

[ndindynd]

My car (09 335i) is beyond due for new o2 sensors. I'm finding the bank 1 for about $90 and the bank 2 for about $150. I thought the sensors were identical except the color of the connector and a few extra inches of wire on the bank 1. What's actually different between the 2 or can I just use 2 of the lesser expense sensors and call it a day? It's not worth $60 just to have the right color connector! And of course does anyone know of a cheaper place to buy?

Bosch Oxygen Sensor - Upstream

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(4 Reviews)
5 Stars

Our List Price:$90.43


Quantity:

(99) In Stock

Part Number: 30048-05267203
Notes: Actual OE Oxygen Sensor -- For cylinders 1-3
Features:

• Advanced Wideband sensing element for exact air/fuel measurement
• Robust sensor design increases sensor longevity
• Sealed protection tube due to 100% functional quality test
• 'True Direct-fit' OE connectors and harness
• Pre-coated threads with anti-seize compound right out of the box

Position: Upstream
Condition: New

Universal Or Specific Fit Specific
Oxygen Sensor Type Wide band

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Bosch Oxygen Sensor - Upstream

Click to Enlarge
(Read reviews)

Our List Price:$149.43


Quantity:

(31) In Stock

Part Number: 30048-05452758
Notes: Actual OE Oxygen Sensor -- For cylinders 4-6
Features:

• Advanced Wideband sensing element for exact air/fuel measurement
• Robust sensor design increases sensor longevity
• Sealed protection tube due to 100% functional quality test
• 'True Direct-fit' OE connectors and harness
• Pre-coated threads with anti-seize compound right out of the box

Position: Upstream
Condition: New

Universal Or Specific Fit Specific
Oxygen Sensor Type Wide band

Shipping Options:
Ground

[nevan]

I am pretty confident that they are the same. Even the plugs are the same. Perhaps, bank 1 precat would be slightly longer (which means you can use for bank 2 also), but I could be wrong about the length. It's been a while since I replaced o2s...

[Added] Actually I recall once switching the b1 and b2 precats by accident (rookie mistake) and still fit and worked (but the condition of working is debatable for another reason). So there is your answer.

[ndindynd]

I'm thinking there *might* be something different. I was getting codes on my front sensor, have been for way too long. But I was saving up my pennies and the code would self clear from time to time and then come back. And apparently these aren't the $20 o2 sensors I expected so I waited :. The front sensor was marginal, no codes rear and no downstream codes. I found a pair of front in stock, no rears. Installed them, immediate codes (yay because they're not a PITA at all to change). But all the codes were from the rear sensor. Pulled and swapped front/rear to see if the code followed the sensor, immediate codes from the rear again.

I found a new bosch rear for $118 online, ordered it today and I'll swap it in hopefully this week. My car might very well have other issues and I'm chasing the wrong problem, but I'll report back.

[nevan]

I re-read the post... Are the post-cat o2s wide or narrow band in the e90 variations? Since you mentioned you were able to interchange them between pre/post, they must be wideband. I am not very familiar with post-e46 chassis, but I would expect to see narrow sensors for post cat... But I could be wrong.

[ndindynd]

I think the downstreams are typical O2's. I'm only working with upstreams though. Front/rear being cyinders 1-3 and 4-6. I haven't gotten any codes from the downstream sensors so I haven't even looked at them yet. But I know they're a ton cheaper and post cats are just there to monitor the cats, so I'm guessing they're nothing special.

[nevan]

Usually post cat error means your narrow band is sensing abnormalities which means it is working correctly. I was confused what front/back meant (i.e., you meant front meaning bank 1 precat while back is bank2 precat, right?). If so, it sounds like it's your pre cat sensor needs replacement.

[ndindynd]

The new sensor was apparently being hand delivered from Germany by a guy with a row boat, but it finally showed up. I did the swap, again, yesterday. Boy I'm sure glad these things are super easy to get to, otherwise I'd be really sick of doing this. Anyway, so far all is good. Several starts since the swap and about 100 miles, 0 codes.

The other day I hit the interstate and just nailed the throttle, big engine shudder : #1 misfire. So new plugs and coils inbound : it hasn't happened since I cleared codes so it might have been legit misfire from having bad a/f mix for so long, but I have 1 30k on the clock and no idea if they've ever been changed so I'm just going to do them all and call it good.