O2 sensors - what do they do????

[bmw7833]

We have to change pre cat or post cat? There is different length for the sensor as well? How i know which type i need to order?

 

[abuhasan]

We have to change pre cat or post cat? There is different length for the sensor as well? How i know which type i need to order?

by going thru the issue discussed, i've decided to change the 2/pre-cat sensors first
after a month daily drive with faulty o2 sensors.

 

[bmw7833]

by going thru the issue discussed, i've decided to change the 2/pre-cat sensors first
after a month daily drive with faulty o2 sensors.

So now what is the diff after u replaced the pre cat?

 

[IanDaddy]

Dear all,

I got advised by Herbert when i first got my car last 2 months ago to change my 02 sensor. In fact my mileage was bout 130k km and the car is fine buy took some advise and changed it.
I just changed my 02 sensors last week at Albert, WP Auto. He actually brought it in from Singapore for me. Changed 2 nos of pre-cat 02 sensors which according to him is more important then the post-cat. is cost me RM 810, RM 380 each for the sensor and RM 50 for labour. It's OEM from Bosch. Took out the existing sensors and it's also from Bosch as well with same part no. 0258005259. So if price about tat range, senang ask albert buy from Sing and go pasang there. Maybe you all GB then can be cheaper too.

Some photos for you all to see see look look. Old sensors on left pic, installed sensors in middle pic and new sensors at right pic.
View attachment 18198View attachment 18199View attachment 18200
Happy Chinese New Year to you all.

Feel any difference after the change ? Responsiveness , Fuel economy ?

 

[abuhasan]

So now what is the diff after u replaced the pre cat?

only now decided to change only pre-cats, bro after went thru' the feedback from all mmbers.
thanks to ALL.
try to squeeze free time todo it by tomorrow.

 

[zidee]

Thanks. Will look into it. Any advise on procedure to open and clean the MAF?

Zidee,

The after cat 02 sensors are not important (just to monitor emission) and won't affect the performance of the car.

As for engine vibrate when it's cold, try to clean your MAF with CRC MAF cleaner.

 

[Herbert]

We have to change pre cat or post cat? There is different length for the sensor as well? How i know which type i need to order?

Replace pre-cat 02 sensors only. If you buy from USA and even though it is Bosch, the cable length is shorter than what we have now. Don't ask me why coz mine I bought from USA. I suggest best is to buy from Bavarian Auto (RM380 each) to avoid any discrepancies.

 

[deep3102]

The O2 sensors for M52 and M54 engines could possibly be different. When i checked with AB, they quoted me RM510 per piece for my M52.

 

[Herbert]

Thanks. Will look into it. Any advise on procedure to open and clean the MAF?

If you are the DIY type, then you should know how to remove the MAF. Spray generous amount of MAF cleaner directly into the MAF aiming towards the sensor. Let it dry for 5 minutes and re-assemble MAF.

If unsure, then ask your workshop to do it for you.

 

[Herbert]

The O2 sensors for M52 and M54 engines could possibly be different. When i checked with AB, they quoted me RM510 per piece for my M52.

Sorry mate, Alex bought his pre-cat 02 sensors (RM380 each) from S'pore through Albert of WP Auto.

 

[deep3102]

I see, thanks for the heads up bro.

 

[IanDaddy]

If you check realoem, the part nos for bank 1 and 2 are different. I think because the cable length is different.

 

[bmw7833]

That's the problem when i want to order oversea, not sure which one is the correct one to order.

 

[IanDaddy]

some online stores do publish the cable length. Compare that to the one in Realoem.

 

[lwloh]

Feel any difference after the change ? Responsiveness , Fuel economy ?

well i did not feel much diff really. fuel economy also roughly the same. maybe just slightly better... slightly.. but always I tekan, susah to judge la. hahaah

 

[ramsing]

sometimes 02 sensor best to buy local. i bought from SG once, it was not working properly. had to get one locally. i think another member also had the same problem as me.

 

[zidee]

I've replace my POST CAT O2 sensor Bank 1 on my Year 2000 E39 yesterday. Erase fault code and never re appear. So now all my 4 O2 sensors (2 pre cat and 2 post cat) should be working fine. I have 1 extra post cat sensor OEM BOSCH brand. Anybody interested I can sell at discounted price. Auto Bavaria sell pre cat at RM370 and post cat at RM390 per piece. PM me for details.

 

[bmw7833]

Bro, when i scan my car, there is no any error code appear, is that mean my o2 sensor still ok?

What kind of error code u got last time?

 

[zidee]

Error will be at DME module. If there is not oxygen sensor error there mean your sensor is ok.

 

[Herbert]

Bro, when i scan my car, there is no any error code appear, is that mean my o2 sensor still ok?

What kind of error code u got last time?

Error codes will only appear when your pre-cat 02 lamda sensors are totally fired. Based on your car's mileage (believe should be over 100,000 km), your pre-cat lamda sensors are already degraded hence fuel consumption is high.