help with o2 sensor wires please

OonDeanisS · Mar 31, 2012

i took my 02 sensor harness out of my 1990 5.0 manual trans. and re-wired the whole harness because it was full of short wires butt-connected all over the place, and i was getting a code for LH 02 sensor. so i made it nice how it should have been all along, but now im not sure what wires to connect to the 02 sensor wires, as each one has 2 white wires and a black wire. does it make any difference if i cross the two white wires? id hate to fry something just by using the wrong white wire.

My engine harness has a blk/grn wire that splits into 2 white wires, one on each sensor.
There is a grey/yel that splits and is black on one and white on the other.
There is a red wire that goes to the RH black wire.

any help differentiating between the two white wires on each of the HEGO sensor would be great! thanks!

87-t-top-gt · Mar 31, 2012

Nope the pos/neg doesnt matter as long as there is one of each. Color wont matter as long as they are same gauge. Just like if you've ever seen a car with two black or two red battery cables...factory ran out of one and opted not to halt production and used 2 of the other.

OonDeanisS · Mar 31, 2012

so youre saying the 2 whites are the pos and neg for the sensor? then what is the black?

87-t-top-gt · Apr 1, 2012

I'm sorry, I missed the black wire part. I'd assume black is the negative(ground) and the whites are a positive(power) and a direct line to ecm. Again, that is a guess. It should not matter one way or another as long as each wire is connected properly and are ~ same size. If you are still unsure, I'm going to be up at the garage working on my car today and can read my manual/diagram and get back to you later this afternoon

OonDeanisS · Apr 1, 2012

thanks, heres a diagram i drew up of my harness as it came off my car. This is as if im looking at the harness from the back side (wires are coming out towards me)... this is the way my harness is wired.... what makes me unsure is the fact that there are two wires (blk/grn and tan/yel) that split into two.

Can anyone confirm this is correct? or explain which pins go to what?

Boss 351 · Apr 1, 2012

I just replaced mine. I highly suggest you find a used one... New is about 130 bucks...

http://www.mustangsunlimited.com/it...&SubSubCategory=Wiring+Harnesses&CatKey=74-01

If not, this site can provide some insights: http://oldfuelinjection.com/?p=6

OonDeanisS · Apr 1, 2012

i re-wired mine, theres nothing wrong with it, i just want to make sure each wire goes to the correct spot.

jrichker · Apr 1, 2012

So far you got lots of advice, and most of it is incorrect. Put 12 volts on the wrong sensor lead and you will ruin the sensor.

One white wire is the 12 volts for the O2 sensor heater, the black wire is the signal & heater power ground, one white wire is the O2 sensor output. The sensor wiring is Teflon insulated to survive the high heat around the exhaust system. Use regular insulated wire on the O2 sensors and the heat from the exhaust will melt or damage the wire's insulation.

The numbers on the sensor body match the numbers on the sensor socket. That shows you what wires are the heater, ground and sensor outputs.

60 is the sensor and heater ground. It terminates up in the engine fuel injector harness with an orange wire that bolts to either the back of the cylinder head, intake manifold or car body. Make sure this is grounded if you want the O2 sensors to work correctly.

90 & 94 are the O2 sensor outputs.

687 is the 12 volt O2 sensor heater power that connects to a fuse link in the wiring harness.

The diagram for the O2 sensor harness is below:
Diagram courtesy of Tmoss & Stang&2birds

OonDeanisS · Apr 1, 2012

thanks that cleared up a lot, any idea where i can get teflon coated wire with a fuse link in it? and would you suggest i buy that one from mustangs unlimited linked above? after all the reading, id hate to get one that doesnt work for me... i have long tube headers btw.

jrichker · Apr 1, 2012

OonDeanisS said:
thanks that cleared up a lot, any idea where i can get teflon coated wire with a fuse link in it? and would you suggest i buy that one from mustangs unlimited linked above? after all the reading, id hate to get one that doesnt work for me... i have long tube headers btw.

The Teflon wire will only be needed on the sensors themselves. If you aren't adding wire to the sensor leads, the regular 105° C automotive wire will do just fine The fuse link can be tested by turning the ignition switch to Run and looking for 12 volts on the gray/yellow wire. Good 12 volts, don't worry about the fuse link, it is probably OK. No 12 volts or some other reading less than battery voltage, you get to go exploring. According to what I have been told, the fuse link is up in the computer wiring harness near where it comes out of the firewall. Trace the O2 sensor harness back to where it meets the main harness and start unwrapping the tape off the harness.

Fuse link wire is available at your local auto parts store. Be sure to solder and heat shrink the splices for the fuse link if you replace it. A regular 10 amp blade style fuse holder and fuse can be used instead of a fuse link, but you still need to solder and heat shrink the splices. Be neat about how you do the job and the blade type fuse holder is a good substitute for the fuse link wire.

help with o2 sensor wires please

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