how do i know what wire is which? I have 2 whites and one black,thanks.
3-wire O2 sensor wiring....
- Thread starter daves66nova
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Whites are heater.
Black is signal.
Black is signal.
The sensor i'm replacing has a blue and a white only.which goes where? thanks.
price 
Dave - So you don't have 3 wires, just 2 ?
yes just the blue and white
If your harness/connector has 3, and the new sensor has 2, it won't work right.
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I think it's the other way around for him. If this was a universal O2 sensor, there should have been a table somewhere in the instructions. It's not easy to read (I had to clue a buddy in on the key to the cipher).
Otherwise, I agree with mechtech. It can't ever work right.
While is might be apparent to someone more clued into the evolutions of 02 sensors ..
..what is this on?
3 wires are heated ..but two wires probably aren't grounding type. That is, one wire gets reference voltage and the other goes to the PCM. One wire O2's have to ground through the sensor.
I'd check which wire on the 02 has continuity to ground. I would REASON (I do not know) that the heater would be grounded through the sensor since it doesn't have it's own dedicated ground (4 wire - probably switched on or off as required). The other two wires should be your reference and intelligence voltage wires. I don't think that they have a need for a given polarity.
Otherwise, I agree with mechtech. It can't ever work right.
While is might be apparent to someone more clued into the evolutions of 02 sensors ..
..what is this on?
3 wires are heated ..but two wires probably aren't grounding type. That is, one wire gets reference voltage and the other goes to the PCM. One wire O2's have to ground through the sensor.
I'd check which wire on the 02 has continuity to ground. I would REASON (I do not know) that the heater would be grounded through the sensor since it doesn't have it's own dedicated ground (4 wire - probably switched on or off as required). The other two wires should be your reference and intelligence voltage wires. I don't think that they have a need for a given polarity.
It's for a 95 Camry
Is this the post-cat sensor on a 4 cylinder Camry? That is the only 2-wire o2 sensor I can find on any version of the 1995 Camry.
If so, one of the wires is grounded to the shell of the sensor, and the other is the signal wire.
The sensor you are attempting to replace this with does not have a ground wire. It is grounded through the shell, and only the shell.
You can probably make it work using a hose clamp to secure the ground wire to the shell of the sensor.
You can ignore the heater wires, they don't do anything.
Incidentally, I found an OE-type 2-wire sensor for $50 and a universal 2-wire sensor for $25.
If so, one of the wires is grounded to the shell of the sensor, and the other is the signal wire.
The sensor you are attempting to replace this with does not have a ground wire. It is grounded through the shell, and only the shell.
You can probably make it work using a hose clamp to secure the ground wire to the shell of the sensor.
You can ignore the heater wires, they don't do anything.
Incidentally, I found an OE-type 2-wire sensor for $50 and a universal 2-wire sensor for $25.
Originally Posted By: brianl703
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If so, one of the wires is grounded to the shell of the sensor, and the other is the signal wire.
The sensor you are attempting to replace this with does not have a ground wire. It is grounded through the shell, and only the shell.
You can probably make it work using a hose clamp to secure the ground wire to the shell of the sensor.
You can ignore the heater wires, they don't do anything.
Incidentally, I found an OE-type 2-wire sensor for $50 and a universal 2-wire sensor for $25.
? If one goes grounded to the shell and i ignore the heater wires,then which goes connected to the wiring harness?
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If so, one of the wires is grounded to the shell of the sensor, and the other is the signal wire.
The sensor you are attempting to replace this with does not have a ground wire. It is grounded through the shell, and only the shell.
You can probably make it work using a hose clamp to secure the ground wire to the shell of the sensor.
You can ignore the heater wires, they don't do anything.
Incidentally, I found an OE-type 2-wire sensor for $50 and a universal 2-wire sensor for $25.
? If one goes grounded to the shell and i ignore the heater wires,then which goes connected to the wiring harness?
Do the following.
Take a multimeter and, using your old sensor, find which of the two wires is connected to the shell. That's ground. This is most likely the white wire.
The other wire is signal. Most likely the blue wire.
What I said before still applies...black on your new sensor is signal and the two white wires are for the heater and do not need to be connected to anything.
You WILL have to take one of the wires (probably the white wire) from your harness and ground it to the shell of the o2 sensor.
The other wire, probably the blue wire, gets connected to the black wire from your new o2 sensor. The two white wires from the new sensor are left disconnected.
Take a multimeter and, using your old sensor, find which of the two wires is connected to the shell. That's ground. This is most likely the white wire.
The other wire is signal. Most likely the blue wire.
What I said before still applies...black on your new sensor is signal and the two white wires are for the heater and do not need to be connected to anything.
You WILL have to take one of the wires (probably the white wire) from your harness and ground it to the shell of the o2 sensor.
The other wire, probably the blue wire, gets connected to the black wire from your new o2 sensor. The two white wires from the new sensor are left disconnected.
Well, i finally got around to checking the old sensor with an ohmmeter and it none of the wires showed 0 when i checked it to the shell. Does it mean that it's been dead?On the new one,2 of the wires showed continuity ,but nothing checking the wires to the shell.I even checked both wires together on the old one and nothing.
First..your new sensor does NOT have a wire grounded to the shell. You have to add one.
Second, your old sensor may have a ground wire that is not connected to the shell.
The 2 wires that show continuity on your new sensor are the heater wires. You will not be needing those. Your old sensor didn't have a heater in it.
Since your old sensor does not have it's ground wire connected to the shell, all I can suggest is getting a digital multimeter and a propane torch and connect it up and see if you can get a reading out of the two wires when you heat the sensor to red-hot with the torch. The reading (which will be less than a volt) should tell you which is ground (negative) and which is signal (positive).
If the multimeter displays a negative reading when you do this, the wire connected to the meter's + terminal is ground on the sensor.
Second, your old sensor may have a ground wire that is not connected to the shell.
The 2 wires that show continuity on your new sensor are the heater wires. You will not be needing those. Your old sensor didn't have a heater in it.
Since your old sensor does not have it's ground wire connected to the shell, all I can suggest is getting a digital multimeter and a propane torch and connect it up and see if you can get a reading out of the two wires when you heat the sensor to red-hot with the torch. The reading (which will be less than a volt) should tell you which is ground (negative) and which is signal (positive).
If the multimeter displays a negative reading when you do this, the wire connected to the meter's + terminal is ground on the sensor.
Can i also check them after a good drive? Or maybe hook them up and see if the check engine light comes on? I don't have a torch.
Since it's the post-cat sensor it probably won't generate much voltage at all when it's installed, unless the cat is worn out. Still, you could check it at idle with the engine fully warmed up.
I tried to take the post sensor off.Tried dang hard! I noticed it says toyota on it! Never changed!
I drove it for a while and i checked for voltage soon after,nothing. I also disconnected the sensor wiring and drove around for a while to see if the check engine light would come on and nothing.What's the easiest way to take this frozen sensor off?
I've never had an issue removing an O2 sensor..so I can't suggest any tips for that. Did you try it with the exhaust hot?
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