Wiring a Heated 02 Sensor


Keepin' The Shiny Side Up
Dec 30, 2001
Im going to try running a Bosch 13942 02 sensor, with 3 wires on my TRs. Obviously one of the white wires goes to the factory single wire, one goes to ground, and the other is a 5V reference. Where can I tap into this reference at? Best place, etc. This is going to look as factory as possible with spliced in connectors and such. Thanks for the help. :)
The positive is actually a 12v reference. I tapped into the fuel pump relay wiring on the RH side fender apron rail. Most of the other sensors use the 5v reference like the TPS, etc.
Hmm, I wasnt aware that the 02 needed a 12V ign/reference voltage, thought it would just need 5V like most of the other sensors. Okay, so I can use any 12V ignition lead? What would be the best place is what Im asking. I already have lots of wires coming off of the alternator (headlights, fuel pump, alky). Anything close? What about the FP IGN lead that we use for the hotwire relay on the drivers side, grey connector? Will that work?
Just checked my old ATR heated O2 directions and the wires are 12v+(red), ground(black), and signal(white). They don't use a "reference" voltage that is modified and sent back per-say. Look at the OEM O2 sensors, they only use the one signal wire. The three wire setup differs only due to it having an internal heater.

Any source of power that is hot in the run position. Don't use the alt post as it's hot all the time since it is connected directly to the battery. Use the hot wire connection on the output side of the relay or the OEM fuel pump relay output wire like I did. That one is the nearest one I can think of. I think there is power at one of the EGR wires as well. Check for 12v+ with a test meter.
Thanks Mark........

I think Im going to just run a wire into the fuse box to the IGN port. However, I will poke around with my DVOM and see if I cant find a better source for the 12V IGN.

The 02 Sensor Im using is out of a 91 Mustang GT, 3 wire, 2 white, 1 black. It has a square plug with obviously 3 prongs. I will be using the opposite end of this 02 (cut from a junk yard car) to make it plug and play. I will also use the end of a 1 wire bosch that I have laying around to splice into the other end of the junk yard plug so I do not have to cut the factory 02 wire, simply plug it in and go.

Hopefully I will be able to tell which wire is signal, and which wire is hot from the junk yard plug..............
I used to run the exact setup. The only thing is, I had one white to 12V, one white to ground, and black to factory O2 plug. I always got good readings. I wonder if I had it wired wrong?