I picked up a heated o2 sensor today for a 4th gen. It has 4 wires..pruple which I know is signal...one tan, and 2 brown. Which is what out of the other 3 wires?

Thanks

Jester,

For reference, three-wire HO2S can be connected as follows:



I'll try to come up with the four-wire circuit for ThirdGens...

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Later,
Vader
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Justice and Freedom will Prevail

[This message has been edited by Vader (edited September 15, 2001).]

Thanks much for the reply Vader..but it really doesn't do me any good.

I don't have an ECM, or an evap purge, and I know how to wire a relay

I just need to know which color wire is what on the 02. I dunno what do do with the 4th wire

Jester,

If my suspicions are correct, you should be able to meter resistance from the tan wire to the sensor body (ground). You should also be able to measure resistance between the two brown wires (heater elements) but from niether wire to ground, nor the tan wire.

If that is correct, the two brown wires are the heater element connections, and the purple wire and tan wire (ground) are the sensing element connections.



------------------
Later,
Vader
------------------
Justice and Freedom will Prevail

...or, if it is for a mixture monitor:



------------------
Later,
Vader
------------------
Justice and Freedom will Prevail

4 wire O2's have a double ground. Dunno which kind of O2 you have, but the 4 wire one I have (On a Honda....stop laughing!)
is as follows.....
White = signal to ECU
Green = 12 volts for heater
2 Blacks = both are grounds.

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

Mr.

While that may be true of NipponDenso sensors, the Bosch 4-wire sensors have an isolated heater element and are connected as shown above. There is one ground connection to the shell used for signal reference. The PCM actually modulates and controls the heater current on North American GM cars, maximizing useful life of the sensors.

Honda may or may not modulate or duty-cycle the heaters - I don't have any knowledge of how they are supposed to operate. ¿?

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Later,
Vader
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Justice and Freedom will Prevail

Thanks Vader...you're the man as usual.
This one looks liek exactly what I need.

Vader....
I'm using a Bosch in my Honda now. It came with the "proper" color wiring for a Honda.
I do know for a fact that the heater is on full time when car is on.

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph