I stumbled upon this email on a MB chat board regarding using a "Universal" O2 sensor and a 90 Ford mustang sensor in leiu of the 2 X $100+ BMW units that are needed on my 94 530iT. Haven't looked into this yet, but figured i share in case anyone out there is interested or can attest to the accuracy of this "Trick".
....On my BMW 325e, the three-wire O2 sensor is mounted close to the Catalytic (under the car). The extra two white wires are to engage
an electric heater embedded in the O2 unit in order to help it heat up faster when you start the engine cold.
I have found (through conversation and research) that a Bosch O2 sensor designed for the exact fit in a 1990 Ford Mustang (w/ 5.0 liter V-8
engine) has metric threads (with a little Anti-seize already on them), and virtually is the same sensor unit. The only differences between the Ford sensor
and the BMW sensor is ...
(1) the end connector and length of wire
(2) name of the car it goes into - based on the salesman's computer
If you do indeed have the One-wire type, Don't by the BMW replacement but ask the sales counter man for the Bosch "universal replacement" unit. This
is YOUR O2 sensor with one 36" wire with no connector on its end and no embedded heater. The connector is only a spade push connector that you can get
anywhere; or use your own. Cut off the excess wire, crimp or solder on the connector, Install and you're off. The cost for the universal One-wire
connector is ~ $29. The BMW one is about ~$79 at Autozone and over $100 at a dealer.
However, if yours is the three-wire type, (with two white heater wires), Bosch does not make a universal Three-Wire O2 sensor, because they don't
trust us DIY'ers to get the connections correct. So they place the manufacturer's mating connectors on to the wire ends. This makes a typical
3-wire Bosch a "Ford Mustang" unit with the Ford connector (at ~$39) or a "BMW" unit with the BMW connector (at~$150).
Hey! "There can't be a $110 cost difference in just the connectors?!?!?! I smell a ripoff.
So I have made the 1990 Ford Mustang 5.0L my universal 3-wire O2 sensor. Just simply cut-off the Ford connector and solder the existing BMW
connector on to it (while matching wire colors), and install. Tell the Autozone man that you have a "1990 Ford Mustang V8 5.0L" He may have 2 or 3 different
Bosch part numbers to choose from; (the only difference is the length of sensor wires, 18", 24", or 36") Since you are not using the connector,
you don't need all that extra wire anyway. So just tell him that you want the cheapest one and that you don't care about the wire length. You might
get some funny looks here because he wants to make sure that the unit you buy will reach the socket it mates to; but you still really don't care.
Also, he might want to sell you 2 sensor units because his computer screen says that the Mustang requires 2 sensors (for dual exhaust). Just tell him (with a
grin) that you only want one today and that you will get to the other side in the winter. Again more funny looks! Take it home, splice wires, and
try it 0ut for 1/4 of the cost.
This Ford unit works well in both my 86' BMW 325 and my 89' Volvo 740. If for some reason you car has the Three-Wire type, get yourself the Ford
Mustang one also. . . .
Rodney, I am pretty sure that it wouldn't hurt to try this on you MB
(just like my BMW and Volvo). If you can manage to remove your sensor and take it
with you to Autozone, PepBoys, etc. for comparison against the Ford Mustang unit you can be really sure that they are mechanically the same. IMHO, I
feel that its worth a try for ~$39. OTOH, this action may be frowned upon by many who would only use genuine MB parts and accessories.
Let us know how your O2 adventure goes.
86 BMW 325e (Bosch O2 designed for Ford Mustang w/spliced BMW connector)
89 Volvo 740 GL (Bosch O2 designed for Ford Mustang w/spliced Volvo connector)
85 MB 380SE (Bosch universal replacement 1-wire type @ ~$29)