View Full Version : Anybody have wire colors for the O2 sensor on the harness side of the plug??

10-03-2014, 02:28 AM
As the title says, does anybody have the wire colors for the harness side of the O2 sensor harness? I know the wires on the sensor are Blue, White, Black and Black. I need to know what the colors are in the harness.

My luck is continuing. I'm still getting the 21 and 54 codes from my 3rd gen conversion. I had a few minutes this evening and decided to check the O2 sensor to see if I had a loose wire or something. Sure enough, not one but two wires broken off at the plug. While looking at it, a third one come off. While looking at that and trying to figure out if it was possible to get the wiring back in the plug, the fourth one came loose. So now I'm holding the damn plug with four loose wires and not know how they're supposed to be connected to the sensor.

In Toyota's infinite wisdom (and to be fair, like most car companies) the wires on the harness side of the plug ARE NOT THE SAME colors as the wires on the sensor. To make things even easier, the wires shown in the Toyota wiring diagram for the 92 3S engine don't match what is on my car and as far as I know it's the original harness. The factory wiring manual shows a Pink/Black wire going to one of the heater wires (black on the sensor), a yellow looking wire going to the other heater wire (also black on the sensor), a white wire going to the signal wire (Blue on the sensor and a brown wire for the ground (white on the sensor).

On my harness, I do have what appears to be a pink/black wire. I also have what appears to be a white wire. The thread wire also appears to be white and finally I have a black with a white stripe (at least I think it was white). So I hooked the pink/black wire up to one of the black sensor wires, the white wire up to the blue sensor wire, the other white(?) wire up to the other black wire and finally the black wire up to the white sensor wire. The black wire in the harness is also a heavier gauge than the other three. Any way started the car up and after a few seconds the CEL come on again. Still showing the 21 code. I'm guess that the way I hooked it up is not correct.

I'm guess it's probably something to do with the white wires and the black wire. I'm pretty sure the pink/black wire is in the right spot. The wire going into the HT spot on the ECU plug is pink/black. The one going to the OX spot on the plug is white. I'm just not sure that I've got the right white one and further is the other white wire the ground wire and the black wire for the other side of the heater or I am missing something completely.

Hopefully someone has the color codes. I guess it's possible that I've got a JDM harness as the engine was swapped out by a PO but based on some of the other things they didn't do, I'm guessing that's not the case.:blink:

Thanks in advance.

10-04-2014, 02:03 AM
Shouldn't need a wiring diagram. Ohm out the wires.
Signal wire also goes to the DIAG box. See which one has continuity.
Ground wire is ground.
Heater power wire is 12V with the key on IIRC.
Heater ground is grounded through the ECU.

10-04-2014, 02:05 AM
You might also have a problem with the O2 signal wire in the harness. It get's really brittle and can break [get's moved any time the harness is moved for belts, T belt, ect] where it "elbows" by the alternator.

10-05-2014, 10:23 PM
Got them sorted out. Once I got the right white wire for the signal and found the 12V wire for the heater things went well. The pink/black wire is the one that feeds signal back to the ECU, the black/grey wire was the 12V wire and the other white wire the ground.

No code 21 now. Thanks for the help Jeremy!

10-06-2014, 04:29 AM

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You will have better luck posting your own thread, since this thread is from 2014.