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1998 BMW 740i

Question: Bank1 Sensor 1 o2 sensor location

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opmax123, Vernon Hills, IL, March 12, 2011, 09:10
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I am getting conflicting information as to the location of the bank 1 sensor 1 oxygen sensor for my bmw 740i. I am told bank 1 is the side of the engine that cylinder #1 is located. I am also beeing told b1 s1 is located on the passenger side of the vehicle. and to top it off I am being told cyl #1 is on the drivers side. So what is the true story is the b1 s1 located on the passenger or drivers side? and is cyl #1 located on the passenger or drivers side? In other words which side of the engine front sensor should be replaced?

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  • Answer #1

    ZeeTech March 12, 2011, 10:37
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    Bank 1 is where #1 cylinder is.
    The Bank 1 is the right / passenger side. The cylinders are (from the front to back) 1-2-3-4
    The Bank 2 is the left / driver side with cylinders 5-6-7-8.
    The sensor 1 is located BEFORE the catalytic converter (between the engine and the cat. converter).
    At this age I suggest to replace all 4 O2 sensors, not only one - BMW recommends to change all @ 100K miles anyway. I also suggest to use OE parts, for the "universal" O2 sensor -without the connector- you will just waste your money.

    Zee

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