The universal O2 sensor I got from FCP has 2 black wires, 1 blue.

The original of course has 2 white wires, 1 black.

Any idea how to wire it all together?

By the way, the sensor came with wire connecters, heat shrink, and a little tube of antisieze.

Thanks, Greg

make sure you try to keep the length of the wire to connector at firewall the same as original. While very small, the resistance in the wire is essential for proper operation.

Since you're into the "fine points" here, I thought I'd bring up another topic. I've seen stated that the sensor won't work if you solder the harness connections onto it; that you must crimp them only. I believe it was stated that the sensor works by detecting a difference between oxygen levels between the top and bottom sections, and that non-soldered wires allowed oxygen between the conductors, so it could get into the top of the sensor.

This seemed a bit far-fetched to me - comments anyone?

I too used to be obsessed with keeping the O2-sensor connections as 'clean' & resistance-free as possible - especially considering the low voltage and current involved.

However - consider the fact that if resistance was so critical, the O2 sensor would have had a separate ground connector for it's output, rather than tapping it from what is probably the most rust-prone connection: via the exhaust manifold body. Seems like any care taken in ensuring a 'clean' +ve output connection will be offset by the ground-resistance involved.

Noel

o2 sensors do not use a ground through the exhaust to generate a signal to the ECU. Therefore, it is irrelavant.

And by the way, the instructions recieved with a Bosch universal O2 sensor, is to keep the wires, including wire crimp the same length as original being replaced. I would be under the presumption that Bosh knows what they are talking about for whatever reason.

bosh mite know but u dont - good ground issensial for volt refrense any other load thro ground path shifts what ecu sees - bosh wants u to keep wires same long for fisical protect not resistence

You are on target in my opinion. The resistance in the sensor circuit is negligible compared with the input impedance of the ECU. But the voltage is small and easily influenced by a ground loop caused by something sharing the same current path as the exhaust system to ECU, which includes the engine to body strap on older 200 series cars. Just a hundred millivolts difference would affect the switch point on the sensor's output. Later systems used a four-wire sensor providing its own ground return.

On the other hand, the resistance of the heater circuit is an appreciable part of how effective the heater is, so extending these wires with unreasonable lengths or inappropriate gauge and poor connections could keep the sensor out of its designed temperature range. You'd have to push your imagination to envision this being a problem with even the most adventurous do-it-yourselfers.
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Art Benstein near Baltimore Crrrrazy Ray's!

Excellent point.

Jeff Pierce
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'93 945 Turbo ( one kickass family car ! ), '92 Mercedes 190E (my daily driver), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece -- sold to a loving home), '85 Jeep CJ-7 w/ Fisher plow

>While very small, the resistance in the wire is essential for proper operation.

How so?

This seems to be a myth to me as well, at least thats what I conclude from the classes I took to become an electrical engineer. There is a resistence per foot of the wire but it is quite negligible.

The ECU looks at the voltage it sees. The voltage drop due to the resistence of the wire is equal to the current times the resistence. I'd guess the current is in milliamps and I'm certain the resistence of the wire to be much, much less than 1 ohm. SO... the voltage drop would be in the milivolt range and that is a conservative estimate.
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Paul NW Indiana '89 740 Turbo 110,000

The 2 wires of same color are for the built-in heater element. Polarity not important.

thanks for the replies...I figured out (by reading the directions that came with it!) which wires went where. two whites went to two blacks, and one black went to one blue. My new harness is identical to the old within the length of the crimpers. If that's not good enough then they shouldn't offer a universal replacement. I used the crimpers and heat shrink only, and wrapped the new package in electrical tape. we'll find out, I'm going back for inspection next week.

It should work out fine. Don't worry about the length; if there is any instruction regarding that it is to keep someone from using so much they have to coil up the excess somewhere it would easily get damaged in a snowbank or whatever. Instructions geared to replacement parts don't come with explanations of the whys and wherefores.
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Art Benstein near Baltimore Crrrrazy Ray's!