This is quite an old thread but am reviving it now to share my experience regarding the o2 sensor issue.
I purchased my Swift last year in January and after driving it for around 4 -5 months without any problems Alhumdullilah, one day the check engine light came on while I was going out of a workshop after I had got my bumper fixed because it was lose. That was a 3s dealership so the foreman took a look and checked everything thoroughly and over the course of a few days fixed the engine light issue.
What he had done was simply used the disconnecting battery method and it had worked so I was happy and didn't think much of it. After a while the light came back on and so they connected the computer and told me that there is an issue with the o2 sensor but its nothing serious and we will tune the car as tuning was due too and use the disconnect battery method and hopefully the check engine light should go away which it did... for a good 7 months.
A few weeks ago the check engine light came back on. Now I was already familiar with the issue so I tried the battery disconnect method and it worked for a few days. But at the back of my mind I knew that I shouldn't be neglecting this issue and get it checked with a computer at least just to know if there is another problem or not.
So I went to Suzuki Cantt Motors on Bedian Road. The Foreman there (Malik) is a very good man and he has really worked on my car to my satisfaction and done whatever I have asked him to do, moreover he has literally answered any and all questions that I had but I will explain that in detail later.
The first thing they did was connect the computer and see the readings.
Now the error that came on the computer was "P0031" which is an oxygen sensor error.
This is when I was told that this error is caused because your oxygen sensor is giving a false reading and it could be faulty due to various reasons. Two of which may be that the voltage circut going to the oxygen sensor was low or the wire was not earthed properly. He said first I will check these possibilities and if they are okay then we will have to change your oxygen sensor.
After I came back home I did a basic search on the error code and realized that he was absolutely spot on about the errors and was very surprised at his honesty.
After spending a few hours on google and YouTube and conferring with my elder brother who is an expert in these matters, it became clear as daylight to me that the oxygen sensor is an extremely delicate and sensitive component and it shouldn't be replaced from Bilal Ganj or Kabali or wherever but always with a new one.
This is because the oxygen sensor detects and measures the proportion of oxygen that is being made inside your engine. It then sends those readings to the car's ecu and the ecu then determines how much fuel should be squirted out from the injectors etc. Having a correct oxygen sensor is vital in giving your engine a longer life and saving fuel.
If the Oxygen Sensor isn't even doing its job properly in the first place then god knows what can go wrong with your car later on.
That's why always get a new oxygen sensor.
The people who replace an oxygen sensor with a used one should do it on their own peril. This might seem like any other component to you guys but this is not like a headlight or a loose gas tank kay replace ya welding kara kar theek ho jai gi
Anyways I had made up my mind to order a new one from the 3s dealership itself so I placed an order day before yesterday and made half payment. The new one should be getting delivered today or tomorrow so I will update with the details later.
This is my oxygen sensor story so far ...