O2 Sensor Install DIY (4-Wire, PreCat, NB. 1.8)

[XM_Rocks]

Why I wrote this DIY:

In my opinion there is no good detailed photo DIY on here or the big board for brains like mine.

I know with these types of installs there are always things if not done in sequence can cause the repairer to have to double back and undo some steps.

This is meant to take you step by step through the process.

This may help you to side step my procedural follies.

So ignore some of the pictures that have items in the background that may look out of order.

I am also far from an experienced mechanic so any suggestions or things I missed or left out should be pointed out!

Tools Needed:



1) O2 Sensor - Bosch 15733 or O2 Sensor with Miata specific with matching harness

2) Solder Iron

3) Solder

4) Stubby Ratchet

5) Large Ratchet

6) Permatex Anti-Seize

7) Electrical Tape

8 ) Floor Jack or Widow Maker

9) Jack Stands (1 Minimum, 2 or 4)

10) Work Light

11) Knife and/or Scissors

12) 22mm small open wrench head (Picture below, found set at Autozone)

13) Penetrating Oil (Not in picture)

14) Eye Protection (Not in picture)

Here is that open wrench that is a life saver:



Nice to haves:



1) Creeper (oh boy... $30 well spent. I am just trying to stimulate the economy. This saved my back!)

2) Wire Stripper

3) Mechanics Gloves (Not shown)

[XM_Rocks]

Instructions:

All references to "O2 Sensor" below is only referencing the Pre-Cat O2 Sensor.

Step 1: Locate O2 Sensor

The O2 Sensor is to the rear of the front driver-side suspension.

- You can actually crack your hood on an NB and see it if you follow the exhaust pipe out of the manifold down to where it goes underneath the firewall on the drivers side.

- You can also see it by cutting your wheels to the right and peeking at it behind the front wheel on the driver’s side.

Here is the O2 Sensor looking down from the engine:



Here is the O2 Sensor from beneath the car looking from the front suspension:



You could probably do the whole thing from above... however I did a combination.

Step 2 - Jack up the car

Use existing DIY on the big board and common sense.

Jack up the car. You can either jack up the driver’s side front, all of the front or all four corners.

I chose to do all 4 corners. Just because at first I thought the O2 was buried in the middle when I got a look at how the catalytic converter was so far towards the middle. It also gave me a good opportunity to get acquainted with my car.

Once you have jacked up your car and it is secured via jack stands you are ready to move on to step 3.

[XM_Rocks]

Step 3 - Put penetrating oil on O2 Sensor at bung

You may be able to skip but the O2 sensors I have done in the past have been in there pretty good. I was able to get to this step and quit for the day since my wife and I had plans. This allowed it to sit overnight. Normally 5 minutes - 15 minutes is enough.

Step 4 - Loosen O2 Sensor

Take the 22mm wrench head and your large ratchet plus any adaptors... the 1/2 to 3/8's gave me a nice little bit of room.

Anyway get under the car and attach the 22mm open head wrench to the O2 Sensor and stick the ratchet up towards the engine opening.



Then get out from under the car and grab the ratchet end from inside the engine compartment. This will give you enough leverage to probably get it loose... remember lefty loosey, righty tighty.



Mine came off pretty easy.

Step 5 - Removing O2 Sensor

After loosening go back under the car. When you start turning the O2 it will be difficult to turn do to the wires twisting. Feel free to cut the wires at the O2 Sensor so it can be turned easily.



Go ahead and twist the O2 sensor out.

ITS OUT!!!!

[XM_Rocks]

Step 6 - Removing the O2 Sensor wire from the two clips

While you’re still under the car the first clip can be easily traced up.



Then the other clip is behind the engine accessible from the engine compartment. That plug is the O2 sensor plug... the plug with the small blue wire running into it.



Step 7 - Prepping new O2 Sensor

I noticed that the heat wrapping on my new O2 Sensor was sagging. So I zip tied the heat wrapping to the base.

Old vs. New. Of course cut off the excess zip tie.



Take your new O2 sensor and put some Permatex anti-seize on it. It will make removal easier for those who come after you.

Like so:

[XM_Rocks]

Step 8 - Putting in new O2 Sensor into O2 bung

Don’t do any wiring at this point. If you do the wire will twist around and you will have to undo the sensor plug. Don't ask me how I know.

This step is going to be similar to Step 5, with the exception of the install.

Take your new O2 Sensor and get underneath the car (again you might be able to reach it from above, however I liked the control of being close).

Screw in the O2 sensor by hand until it gets tight.



Then like above set your open wrench head attachment to your large ratchet (a few turns with the stubby ratchet is optional). Once it is set up ascend to the engine bay and give it a few good cranks until it is very tight.



*I will add torque specs later for you fancy engineer types. Of course you probably wont be reading this!*

It is what I think of as a non-critical / a piece that won’t cause death if not properly torqued. I hand tighten and give it a turn until very tight.

[XM_Rocks]

Step 9 - Wiring in new O2 Sensor

Start by feeding up the wire from the new O2 Sensor from the bottom into the engine compartment.

If you have bought the fancy O2 sensor with our matching plug, plug her in and skip to Step 11. If you bought the generic 15733 or the 15730 please proceed.

Ok if you are like me you are still with me... wiring... pfft I will do it to save $100!

Now you need to know the wiring for your new Bosch and your car. This is where I have to give a disclaimer that you can try mine if it does not work you may need to source better instructions specific to your car. You are about to see that you will be 50/50 with a random guess. Pretty good odds eh?

************************************************** *

Here is the wiring for my car:

Wire Type / Miata / Bosch
SIGNAL / BLUE / BLACK
GROUND / WHITE / GREY
HEATER 1 / BLACK / WHITE
HEATER 2 / BLACK / WHITE

************************************************** *

Start by cutting the factory O2 wires coming out of the connector towards the drivers side of the engine compartment. Leave about 8 inches of wire.

Like so...



Then strip both the wires from your new O2 sensor and the old wires.

Like so...



So now you have all of the wire exposed.



You can connect these wires one of two ways. One is by using the connectors that they provide or by soldering them together.

My plan was to solder them and see if they were solid under some mild tugging. If not I would try the Bosch connectors.

Here are the connectors:

Save them just in case you need them for later.



I soldered them and was quite satisfied with the connection and strength so I left it alone.

I used a clothes line clip to hold the wires at bay as I soldered them.

Here are some pics of the soldering... look at the great engine soldering iron holder. That’s what it is for right?





Ok time to wrap some electrical tape around the mess you call a soldering job.

Of course wrap each one individually.

Being as non-technical as possible I had the wire in an upside down V.

This helps because when you clamp them in to the top clamp it wont move or separate.

[XM_Rocks]

Step 10 - Clamp down O2 Sensor Wire

Do the first clamp behind the engine... remember what I said above... get the upside down V in there so the wires wont move. Also feel free to zip tie them together right below.

Clip is shown in background.



Now do the clip towards the bottom. Yes the last time you will probably get back under the car!!!!



Step 11 - Lower Car from Jack Stands

Use existing DIY on the big board and common sense.

YOU ARE DONE!!!!!

Take her around the block and make sure she does not explode!

[cam76034]

Where was that creeper when I was doing that fuel filter?

Nice writeup.

[XM_Rocks]

Where was that creeper when I was doing that fuel filter?

Nice writeup.

Oh I had it hidden... I didn't want it smelling like gas. LOL