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4 wire O2 sensor White/Blue/black/black
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hhosurfer Offline
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Post: #1
4 wire O2 sensor White/Blue/black/black
Ok off the blue wire with the ignition on I see .406v so to start with and offset of.02v. I would think I would see .408. but I do not. Only .406

I disconnect the unit and read .02v but with it connected to the ecu and o2 they still read .406???

huh????
04-26-2008 03:42 PM
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colchiro Offline
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Post: #2
RE: 4 wire O2 sensor White/Blue/black/black
I failed psychic 101. What kind of car do you have this installed on? Hmm

Rick

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04-26-2008 05:36 PM
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hhosurfer Offline
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Post: #3
RE: 4 wire O2 sensor White/Blue/black/black
02 blazer sorry my bad.
04-26-2008 05:43 PM
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colchiro Offline
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Post: #4
RE: 4 wire O2 sensor White/Blue/black/black
If you're reading .02 volts difference between the red and black connections on the EFIE, then that's a bit too low. I thought they were set to .2 volts initially, which is a good place to start.

If you're connected to the proper wire on the o2 sensor, the voltage from that lead to ground should fluctuate a lot. You can see this by measuring either red or black on the EFIE and use the car ground for the black lead on your meter. I think the red connector on the EFIE is connected to the ECU and the black one to the o2 sensor.

Rick

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04-26-2008 05:54 PM
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hhosurfer Offline
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Post: #5
RE: 4 wire O2 sensor White/Blue/black/black
yes I can adjust the EFIE I can bring it up to .2 but if the value of the EFIE is .2v and the ecu to the o2 sensor is .406 (engine not running) then should I not read .606v then as the engine was started the volatage would jump around.

But in fact when the engine is not running and the efie is connected to the o2 and ecu it still read .406v????
04-26-2008 06:09 PM
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colchiro Offline
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Post: #6
RE: 4 wire O2 sensor White/Blue/black/black
It sounds like you have it wired wrong or are expecting something different from what you really get.

You have to cut the wire from your o2 sensor to the ecu. The EFIE is connected between those two wires and those two wires are also connected to the black and red connectors on the front of the EFIE.

If you have it connected properly and measure from black on the EFIE to vehicle ground, you are measuring the o2 sensor output. If you measure red to ground, that's the output that goes to the ecu. The difference between the two is the amount the output is being changed.

I'm going to let Mike take it from here. He's the one that sold you your unit.

Rick

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04-26-2008 07:30 PM
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mike Offline
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Post: #7
RE: 4 wire O2 sensor White/Blue/black/black
Your explanation is correct, colchiro, thanks.

hho surfer, I'm not sure I understand what you're reporting.

Quote:yes I can adjust the EFIE I can bring it up to .2 but if the value of the EFIE is .2v and the ecu to the o2 sensor is .406 (engine not running) then should I not read .606v then as the engine was started the volatage would jump around.

But in fact when the engine is not running and the efie is connected to the o2 and ecu it still read .406v????

I just don't understand what you're measuring. Please tell me where you've put your meter probes when you're reading .406v.

I do suggest you double check the installation instructions, and make sure you've followed the schematic exactly. Also, you might check out How To Read Your EFIE, and do the tests that it suggests to see if you get the expected readings in that article. That can help us narrow down any problem you're running into.

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04-26-2008 09:05 PM
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hhosurfer Offline
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Post: #8
RE: 4 wire O2 sensor White/Blue/black/black
I will try again. I cut the blue wire on the o2 sensor without the car running the wire from the ecu reads .406v and the wire from the O2 reads nothing. If I connect those wires and then start the car that voltage jumps around.

It seems the ECU sends the signal to the o2 sensor. the o2 sensor fluctuates that voltage.

should there be another wire from the o2 sensor to the ecu?
04-27-2008 02:50 AM
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mike Offline
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Post: #9
RE: 4 wire O2 sensor White/Blue/black/black
I don't know what wire you have there, but it's not a narrow band oxygen sensor. I suspect it's a different device entirely. The narrow band oxygen sensor puts out a voltage to the ECU. If you cut that circuit, the ECU will not put out a voltage. When the engine is running and warmed up a bit, the oxygen sensor will put out a voltage and if the wire is cut to the ECU, you will still see those voltages on the sensor side of the cut. You will not see voltages on the ECU side of the cut.

AFR sensors act like you describe, the but voltages are different. With an AFR sensor the ECU puts out reference voltage to the sensor and the sensor modifies the current back to the ECU to indicate the oxygen content. More or less current on the return line means more or less oxygen. However the reference voltage is either 2.8 volts or 3.3 volts, not .406.

So, bottom line, I don't know what wire you have there, but it isn't an oxygen sensor. Please get the correct wire and try again.

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04-27-2008 10:05 AM
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hhosurfer Offline
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Post: #10
RE: 4 wire O2 sensor White/Blue/black/black
It is an o2 sensor. there are 2 one on each side of the engine. and one after the cat. I was thinking it might be a feed line for volts to the o2. the white wire may be a return volt. the computer reads the feed and return and then makes adjustment to the AFR.

And after being under the car testing these wires the blue has .406v from the ecu to the o2 sensor when the car is not running but the key is on.

THe white wire has a return volts to the ecu when the engine is running. those volts fluctuates just as the blue. (but not the same volts)
(This post was last modified: 04-27-2008 04:01 PM by hhosurfer.)
04-27-2008 03:11 PM
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