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Thread: O2 Sensor for Siemens DME

  1. #1
    Join Date
    Aug 2005
    Posts
    593

    Default O2 Sensor for Siemens DME

    Does anybody know if an O2 sensor for Bosch will work with MS40 Siemens DME?
    oxygensensors.com says a sensor from Walker ( 250-24021) will fit, however in walkerproducts.com cotalogue the same sensor is also shown to fit Bosch DME.
    What I am afraid of is if I buy the sensor, and it turns out not to fit my car.
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  2. #2
    Join Date
    Aug 2005
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    593

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    Part number of O2 sensor in my car is 11 78 1 730 025. One shop assured me that a Bosch sensor 0 258 005 322 (BMW# 11781735710) will fit mine also. They looked it up in the system they were using and it was telling it should be OK. I believed them because their system was also showing Walker O2 sensor 250-24021 to be also compatible, and that is exactly what the Walker products cotalogue is telling.
    http://www.automedicsupply.com/cross...lker=250-24021
    It also says that 250-24021 is compatible with 11781735710.
    It seemed like both the Walker products and the shops system were telling one thing, so I bought it.
    The problem is the connector on that Bosch sensor turned out to be very slightly different to the one on my car! It fits in the exhaust piping but cannot connect to the connector. The connector is 90% the same but two little indents by side. Funny thing is they are identical in shape, its just in my sensor they are sloped upwards, in Bosch downwards.

    I thought of cutting the wires and connecting through my old connector, however the color of the wires is different. My old sensor has two white, one red and one yellow wires. The Bosch one has two white, one black and one grey wire.

    What do you think guys, should I go and cut the wires?
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  3. #3
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    Aug 2005
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    Below is how the Bosch sensor connector looks like. Connector in my car has those indents by the sides sloping upwards, not downwards.

    Picture taken from this PDF
    http://www.ngksparkplugs.com/images/...t_11-16-04.pdf
    Attached Images Attached Images  
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  4. #4
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    Aug 2005
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    sensor in my car looks like this
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  5. #5
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    Aug 2005
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    593

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    I installed the Bosch sensor. At first engine worked fine. But as the temp gauge got close to the middle it deteriorated sharply. I mean really sharply. Fully warmed up it runs the same as when the O2 sensor is disconnected. Black smoke from exhaust.
    My question is, when does the engine starts to listen to the O2 sensors output? If less than a minute, then the O2 sensor is working fine and problem lies somewhere else.
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  6. #6
    Join Date
    May 2006
    Location
    Antwerp, Belgium
    Posts
    552

    Default

    Did you keep white connected to white? Heated O2 sensors should kick in very fast.
    2008 audi A3 1.9tdi
    (former 1991 520i LPG)

  7. #7
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    Aug 2005
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    In my Siemens sensor there is only one white wire, others are red, yellow and black. I was mistaken above, there is only one white sensor.
    I installed the old sensor back. When I start the engine it first runs normal, after a minute or two it starts running rich, black smoke from exhaust. After driving a while with rpms about 2500-3000 it starts running normal. But if I stop and idle for a couple minutes, then rich again. Also turning off the engine and starting again makes engine run rich.
    I ordered a new sensor, an exact match to the one I have from bmaparts.
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  8. #8
    Join Date
    May 2004
    Location
    Japan
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    9,250

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    At first with cold engine, the MOTRONIC runs with a default value of the O2 sensor, it takes over the actual signals when the cat and sensor are heated up. That is approx. 600 degree Celsius or something like that.

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