1999 Hyundai Elantra O2 Sensor Wiring

  • 4 CYL
  • FWD
  • 88,000 MILES
As I am adding a hydrogen generator to my car, I need to identify the wire that sends the signal from the o2 sensor to the computer. The wire choices are; on the computer side of the male/female plug, a black and a red wire which I assume would be the + and - power to the sensor and another red then an orange. I'm betting either the second red or the orange wire is the one I want. On the sensor side of the plugs there is a black and a grey wire that coincide with the red and black on the computer side; then there are two white wires which are obviously the sensor signal wires.

I will be running the wire that sends the signal to the computer through a device that lies to the computer so when the exhaust gets cleaned up with the hydrogen burning, the computer doesn't increase the dwell of the injectors thinking it's running too lean.

In the Haynes Repair Manual, the wires on the o2 sensor side of the plug are labeled as follows: top row, left to right, wires 1 and 2 are both white wires; bottom row, left to right grey wire is #3 and black wire is #4.

Can you identify the wire that sends the signal from the o2 sensor to the computer for me; from what I read, it's either 1 or 2?

Some background information (these are excerpts from posts on a forum trying to get the answer:

One post.
On the 20 Volt scale.
When I took power readings on the computer side of the plug with just the ignition on I got no voltage on two wires which I expected then (aprox.) 2.7 on one wire then (aprox.) 7.2 on the 4th wire (with the multi-meter set on the 20v setting). What happened to the 12v and one small millivolt reading I should have expected?

A second post.
With the engine running:
On the 20 Volt scale
One wire = 0 volts
One wire = 13.7 volts
One wire = a steady.31 volts
One wire varies between.38 and.41 volts

(I apologize that I didn't identify these wires as I didn't think I was trouble shooting and as it turned out, the wire that varies is the black wire which is not the right one. That black wire also appears to have a positive voltage from both directions from the plugs)

Not trying to over burden you with information, I just want to give you all the information I have. You may have a simple answer with none of this. But I cant ignore that I may have a bad o2 sensor even though the CE light isn't lit.

Do you
have the same problem?
Friday, August 8th, 2008 AT 9:20 PM

1 Reply

On the harness side blue/yellow stripe goes to the PCM for the front sensor. Front O2 heat circuit is Yellow/green. Yellow/blue is the ground, yellow/red goes to the fuel pump relay.
Was this
Thursday, August 21st, 2008 AT 5:22 PM

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