ECU side O2 sensor connector wiring

[skelly]

Hey,

The previous owner of my car appears to have had a minor engine fire which damaged the electrical connectors. I don't have immediate access to a dealer for a replacement O2 sensor, so I bought a universal Bosch. I just need to connect the two sides together, but because the original O2 sensor's connector was damaged, I have no frame of reference to know what's right.

What I would like to know are the wire colors for the four signals coming from the ECU. Mine has a circular connector with 4 pins. I've seen some phots around here site here from other models with a rectangular connector which I'd be afraid may have different wire colors. If i'm not mistaken, I believe mine has two black, a red and a white wire going to the connector from the ECU.

According to my Chilton manual there is a pin ordering for the round connector with the tooth faced UP, where they go like this:

/12\
\34/

The manual tells you how to do a number of diagnostic measurements with a meter, but never explains the signal carried on each line.

I can double-check, but I think the wiring was such that:

1 - red
2 - white
3 - black
4 - black

I presumed that the two blacks were heating coil leads, but I'm confused by the old, damaged O2 sensor's connector because it looks like the two blacks on that were connected to 1 & 3. (The old harness was white/blue/black/black).

Thanks for any insight you might be able to provide.

- SK

 

[91gsxboosted]

I did a bosch o2 sensor on my 91 and all the colors from the original plug in were as follows, I just went outside and looked
1black
2white
3gray
4white

When I did the bosch, all 4 colors matched up and it was pretty easy. This was done on a 91 gsx.

 

[skelly]

Those sound like the colors on the O2 sensor side of the connector. I'm looking for colors on the ECU side of it. I'm willing to believe that one of the wires I think is black could be a dirty dark gray or blue or brown, but those wires are pretty clean and I'm about 90% confident that they're both black and red and white.

Thanks for your response...

- SK

 

[skelly]

Anyone else might be able to take a crack at this?

- SK

 

[gotlag]

Just went through this exact issue. Here is the Bosch chart. This should cover it for you. My O2 matched up as "type B". Hope it helps.

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[skelly]

Hey, thanks for the tables - I got the same table with the sensor, and that definitely helps know the signal assignments for each wire on the sensor - but I need to know the signals on the ENGINE wiring harness. The plug is nearly destroyed from an old over-heat or minor engine fire or something from a previous owner. I know that there are two black wires, a red one and a white one, but all the O2 sensor color codes in the world won't match up with an auto-maker's factory engine harness wiring color selections. I need to know for certain which PIN is what signal on the ENGINE- side of the connector. Lessee if I can illustrate it here:
_--_
/ 12 \
\_34_/

I need to know what the signal value is for those four pins on the engine harness - NOT the sensor harness - looking end-on into the connector. I have some sort of facroty manual on CDROM that I picked up on eBay, so I'm going to dig around in there to see if it's documented.

Thanks for the help so far.

- SK

 

[skelly]

Okay, I think I've found what I need here in the service manual I picked up on eBay. It shows the connector's pinout in relation to how it should hook into the O2 sensor itself, and associates wire harness colors with the connector's pins.

It shows the pins as being:
1) Ground
2) Signal
3) Heater A
4) Heater B

I'm posting the relevant portion of the image here in case anyone else finds it useful...

Oh, the other thing I thought was interesting was the oxygen sensor check connector which the documentation indicates is under the dash over by the passenger door. It looks like this could be used as a conveniently available signal source for use with an aftermarket A/F gauge without "tapping" into the ECU harness. I hadn't seen anyone mention that on the board here, so perhaps that it was worth mentioning.

- SK

 

[luv2rallye]

(From DSM Backup manual for 91 DOHC turbo)
The harness side round connector has pin 1 in upper left, 2 upper right, 3 lower left, 4 lower right.
Harness side: red (pin 3 - goes to mpi relay) and black (pin 4 - goes to ground) are the heaters. Black (pin 2 - goes to ground) is signal ground and white (pin 1 - goes to ECU pin 4) is signal.
Sensor side: Every after market O2 has different color wires. The 2 same color wires, usually white (but sometimes black), are the heaters (go either way - they measure about 12 ohms so you can easily find them even if they are not the same color). The other 2 are the signal and signal ground wires. If black and grey, try the harness black to sensor black and harness white to sensor grey. If it doesn't work reverse these two. If you have 2 blacks, a blue, and a white, see here: http://www.dsmtuners.com/forums/attachment.php?attachmentid=48046

 

[skelly]

(From DSM Backup manual for 91 DOHC turbo)
The harness side round connector has pin 1 in upper left, 2 upper right, 3 lower left, 4 lower right.
Harness side: red (pin 3 - goes to mpi relay) and black (pin 4 - goes to ground) are the heaters. Black (pin 2 - goes to ground) is signal ground and white (pin 1 - goes to ECU pin 4) is signal.

This is exactly what I was looking for - thank you!

- SK