The oxygen sensor is a device that measures the amount of fuel and air in your exhaust. The ECU monitors the sensors out put and adjusts the air fuel ratio accordingly. This is the sensor that most A/F gauges get their readings from, it isnt as accurate as exhaust temp readings but for minor tuning purposes it does the job fine. When the Oxy sensor stopps working the ECU would detect it and boost up the fuel mixture, this is as a safety measure to stop the mixture from going lean and hence blowing up your engine.

On newer cars the ECU also puts up the engine warning light, but appernetly on our older cars it doesnt. So you wont know whats happening until you test it your self.

I realsied my oxy sensor wasnt working after I built my self a simple 10 LED A/F gauge, as soon as I connected the gauge to the sensor nothing happened. I took my digital multimeter and measured the out from the sensor, it gave my a -0.0003 reading and I knew it was stuffed.

According to the manual the oxy sensor readings are:

I gave my mate in who works as a mechanic in FORD a call. The OEM sensor cost $230!! The equivalent Bosch sensor was $70,

and the NTK was $55. I called the local laser wrecker and the pricks wanted $85 for a second hand one!!!

The is what the new sensor will look like.

WARNING! DO NOT DROP THE NEW SENSOR!   If you do drop it then put in into the bin and get another one.

Replacing the sensor

Normaly if you have the right tools it'll be a 5 minute job. By saying right tools I meant a long socket with a split down the side so the wire can pass though. I didnt have the socket and neither did the dudes at FORD so I had to remove a few tings to get to it.

This is where the sensor is located:

On the TX3 and other fuel injected lasers you'll find it hanging of the exahaust manfold, most cars have 2 or 3 locted in the cat and the exahust further down.

First thing you have to do is remove the intercooler pipes, so you have access to the exahust manfold.

Then you have to remove the exahust manfold heat sheild screws.

And then pull the heat sheild off, it would be good idea to work on a completely cool engine :|

Here the exahust manfold with the sheild taken off.

Then I had to cut the old sensor in half so I could use a normal socket to remove it.

The sucker was really hard to remove so i had to use a short pipe as a lever to loosen it.

Finally after I removed the old sensor, I saw that it the thread was too long, and who ever put it in must have forced it.This picture show the 2 sensors next to each other, you can actually see where the thread is stripped on the old one.

Lastly screw the new sensor in all the way until its tight, make sure its tight enuff to seal it properly but not too tight jut in case you damage the thread. If it leaks you'll be able to hear a whistling sound, you may also lose a bit of power too.