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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Jul-20-2011, 04:22:55 AM   #1
modeyaka
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Default M3 E46 Pre Cat O2 sensor replacement...

Hi, Just got 55K miles on my 2002 E46 M3 and seems my Bank 2 senor 1 has to be replaced. I think I'm going to do both sensors plus the spark plugs while I'm at it.

Per below, found a great link that described most of the process. http://www.m3forum.net/m3forum/showt...ght=header+DIY

My question... if I follow the above process, to remove the actual sensor:
1. Do I need a O2 sensor tool? or can I just use an open ring wrench?
2. Do I need to remove any other gear in order to get to the pre Cat sensors?
3. Did you guys use Bosch OEM sensors. They run at about $99/sensor from Advance Auto while the BMW rip off parts are about $275-300/sensor?

I ask this because other post (non M3) talk about using a O2 sensor tool and a socket wrench. However, looking at this configuration, the sensors don't seem to be at an angel where a socket wrench would fit? Hence I'm thinking an open ring wrench is needed?

Any thoughts would be greatly appreciated. I will also try to take pictures during my install and post.

Thanks in advance...
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Old Wed, Jul-20-2011, 04:53:29 AM   #2
mpower22
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

Hello, and first of all - welcome to the forum, n00b.

You will have to take the reinforcement plate off to access the B2, S1 sensor from the bottom of the car. I used a crescent wrench to get up in there, but you'll just have to play with different length wrenches to get the right angle on it. I did not use an O2 socket. The B1, S1 sensor can be accessed very easily from the top of the engine after you remove the heat shields.

Definitely buy the Bosch sensors to save some money. Amazon typically has the best price on these. I even went with less expensive Walker sensors for some of the sensors, which also seem to be high quality but you can decide - most go with all Bosch though.
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Old Wed, Jul-20-2011, 10:04:35 AM   #3
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

It may be easier to get to it from the bottom but I replaced this sensor from the top so I didn't have to pay to use a lift. (I don't have my jack and jack stands with me here.) You will need to remove several pieces to access it. A oxygen sensor crows foot socket socket is pretty much required. I used the OEM oxygen sensor so the length of wire would be correct. I think it was about $130 or so from Pelican Parts. There is a small "DIY" for it in this thread: http://www.m3forum.net/m3forum/showthread.php?t=321070

Good luck!
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Old Thu, Jul-21-2011, 12:35:19 AM   #4
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

Great input! Didn't want to attempt this from the top years ago, only changed mine out because I was doing exhaust at the same time recently.
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Old Thu, Jul-21-2011, 12:45:14 AM   #5
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

Guys, Thanks so much for the information. I assume to replace the Pre-Cat Bank 2 sensor, there is no way of getting a regular O2 sensor socket and wrench. Hence why you recommend a Crow Foot wrench, right?

Rgds...
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Old Thu, Jul-21-2011, 01:01:10 AM   #6
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

One more... how quickly should you replace the sensor once the warning lights come on? I suspect it will be ok to drive for a week or so, right?

Many thanks...
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Old Tue, Sep-15-2015, 09:48:55 AM   #7
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

hi guys,
Can you share pre-cat sensor numbers for bosch?
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Old Tue, Sep-15-2015, 12:22:25 PM   #8
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

Quote:
Originally Posted by Fares.M3 View Post
hi guys,
Can you share pre-cat sensor numbers for bosch?
Call up ecs they can tell you the part numbers quickly, theyre also pretty cheap from them.
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Old Tue, Sep-15-2015, 02:15:19 PM   #9
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

I personally use Bosch 15703 sensors. Just cut the old harness and mate it on the new sensor.

they are $25 each (or less) sensor, exact same narrowband sensor as the OE sensor.
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Old Tue, Sep-15-2015, 02:28:41 PM   #10
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Default Re: M3 E46 Pre Cat O2 sensor replacement...

Quote:
Originally Posted by fares.m3 View Post
hi guys,
can you share pre-cat sensor numbers for bosch?
13952 & 13949
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Discussing M3 E46 Pre Cat O2 sensor replacement... in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)