Greetings All!,
I am new here, but have heard good things about this site. I am hoping to get some advice on my wiring issue.
I have a 93 Ranger 4.0 V6, 4x4, 5 speed manual. I had the trans out to replace some gears and the clutch. After everything was reinstalled I discovered the plug harness for the passenger side O2 sensor was between the engine and bell housing. I thought I would be able to splice the wires, but the colors coming from the O2 sensor are different than what is in the crushed harness, which I cut at the bell housing. Any thoughts on how I reconnect these wires are appreciated. Truck has only two O2 sensors.

 

Welcome to the forum

Passenger side is O2 sensor #1
Drivers side is #2

It's important, lol

Easy to reverse these because connectors are the same, and engine will run like CRAP if that happens.

O2 sensors themselves have pretty standard wire colors
It will be a 4 wire O2 sensor

2 wires are for the Heater, there is no + or - polarity, as long as one is + and the other - then it will heat up(work)
O2 sensor makers use White, Black or Brown wires for the heaters
Rangers used Black/white stripe wire as Ground for heater, Light Blue/Orange stripe as + for the heater, this + 12volts comes from Cab fuse panel, 15amp fuse, which could be blown, so heads up.
So if you see 2 white wires on O2 sensor then those are the heater wires, or 2 brown wires


Other two wires do have an order
Orange wire on the Ranger side is the signal return, which is actually reference Ground
O2 makers often use Tan or Grey wire for this

On passenger side O2 the Ranger uses Grey/light Blue stripe wire, it is the voltage wire(drivers side is Red/black, the only difference in the two harnesses)
O2 makers use Purple and Black(not if heater wires are black)


Overall your best bet would be to hit a wrecking yard and cut O2 connector off and splice/solder it to your Cut wires so it would be plug and play

Reason being, an O2 sensor generates its own voltage, .1 to .9 volts, so not a lot, any small defects in either of the two "signal" wires connections will cause Lean or Rich running

 

Thanks for the info Ron. My O2 sensor has 2 white, one gray, one black. My harness has Blue w/ orange strip, black, orange, and gray. I think you have given me enough info. Thanks again!.
Jim

 

Greetings all,
Once again , I wish to thank RonD for the assistance with my O2 sensor. Very knowledgeable guy.
I have a new challenge that I hope someone can give me some advice on.
93 Ranger, 4.0 V-6, AC, 5 speed manual, 4x4.
I had a radiator seam blow on the way home from work and it overheated needless to say. Check engine light came on briefly. Replaced the radiator and thermostat as it was stuck open. Now when first started there is a lot of exhaust smoke and runs very rough. After a couple minutes, starts running normally and smoke is gone. No evidence of water in oil.
Is there a cold start solenoid or sensor that could have been damaged? Last thing , check engine light does not come on now, but it does work.
Thanks all for any words of wisdom.

Jim

 

It is possible the ECT(engine coolant temp) sensor was damaged by overheating, not likely just possible.

But what most likely happened, unfortunately, is that you cracked one of the heads, maybe both.
The 4.0l OHV heads have a weak spot in the casting between the valves.

When you heat up metal it expands, and when it cools down is shrinks, just the laws of physics, liquids do the same thing.
In normal operation head metal expands and contracts daily, even a few times a day and no problems.
If engine over heats the head metal expands more than normal, and because it is held in place by the head bolts it can only expand down, and that's how head gaskets blow.
Head gasket is in between Block and Head, and will be crushed when engine over heats.
So not a "Chicken or the egg" thing, engine overheats then head gasket is crushed and "blows", after that engine will continue to over heat even after cause for original over heating is fixed, i.e. bad radiator or broken hose.
Damage is done.
Thats for all engines

4.0l heads when over heated can also crush head gasket, but because of the metal expansion they can also crack between valve seats, which is similar symptom as blown head gasket.

First thing I would do is to pull all spark plugs out, easy to do on the 4.0l
Look at the tips, you want to see a light brown coloring.
If you see a tip that "looks like new" it is being Steam Cleaned by coolant leaking in.

With all spark plugs out, remove fuel pump relay or fuel pump fuse.
Crank engine, it will spin fast
Feel the air coming out of each spark plug hole, or you may even be able to see it, for coolant spray
Gasoline is turned off, so any fluid coming out is coolant

The rough running on cold start is because coolant leaks in when engine is off, and fouls the air/fuel mix on cold start, spark plug can't ignite it.
As engine/cylinder heats up spark plug can ignite it.
Also as head heats up the metal expands and helps seal the gasket or crack a bit, so less coolant coming in to cylinder.
And white "smoke" goes away

Coolant/water in the oil is a badly blown head gasket, doesn't happen that often with newer gasket material, can happen just not as likely on post 1985 vehicles.

You can do The Glove Test, 100% accurate for cracked head or blown head gasket, also tells you which cylinder(s) are effected
I posted it here earlier: https://www.ranger-forums.com/sohc-2...hanged-152816/


There is a temporary fix for this, Rislone head gasket fix, or similar products.
FIRST you need to do the tests to make sure that is the problem.

Head gasket "fixes" are a liquid glass compound, the compound hardens when exposed to 900+ degF heat, like inside a cylinder, so seals the leak when it is pulled in.
BUT after engine cools down head and block metal contracts so seal is gone.
You have to pour the sealer into rad and leave it there until you have time and money to fix the problem.
It will seal and unseal daily, and works fine, follow instructions.

It won't clog up radiator or heater core, old mechanics tale, lol.

Had a neighbor who used it for 3 years on an old Pontiac Gran Am V6, had to add more of course, until his automatic transmission went out and he scrapped the car, lol.


When you pull the heads you can often see the crack between valve seats, but if you can't you still need to have heads pressure tested at machine shop, also cleaned and surfaced

 

Thanks for the quick response. I think I am going to try the ect sensor first. It has all the symptoms. Really don't want to pull the heads off if I don't have to. Will keep you updated.
One last question. Can you tell me where the sensor is located? Watched some videos and have a vague idea, but......
Thanks again!
Jim

 

The info you provided on the wiring for the o2 sensors has saved my sanity. I had a new motor installed in my 94 4.0 about a month ago, mechanic never test drove and I had problems right away. Assured me he does not make mistakes so anything wrong with it, had to be a pre existing problem. I went thru, tested everything possible, replaced every single sensor under the hood, checked fuel pressure, checked cat, tested all vacuum lines for leaks had multiple mechanics look over it and make suggestions, nothing worked. Kept getting check engine light on and off, was getting lean codes, and then not getting lean codes. Truck had no power in the low end or mid range, but seemed right in the high end other than some pinging and occasional bouts of bad mis firing. So then I started pulling all my harnesses one by one and checking them and cleaning them of any corrosion, and when I got to the o2 sensors, i noticed one wire harness was pulled really tight and the other had excessive slack, so I thought, could it be possible they are backwards? I searched everywhere for a wire diagram, and found this post, and wouldn't you know, they were backwards. Swapped them today and truck runs like brand new!! Thanks so much for your knowledge RonD, my Rangers guardian angel! Lol

 

Good work

Thanks for posting your experience and the FIX