oxygen sensor problem

[ivansi]

Hi,

I am having oxygen sensor trouble that causes the check engine warning light to come on. A plug into the computer says it is O2 sensor bank 1 before cat that is faulty.
However, I have changed both sensors before cat and the cars runs for about 100 miles with the warning light off, then it comes back on again!
If I then have the warning light switched off, I do about another 100 miles then it comes on again!
When the warning light is on the car runs fine - any ideas on how to fix this?

thanks

 

[mic]

Hi, check for leaks or poor sealing of that banks exhaust system, from cold and also when hot.

Regards

Mic

 

[jeegnesh]

check the coil packs have not got splits, I had this problem too, ended up changing both bank sensors, and finally coil packs and the problem has not come back since.

 

[ivansi]

thanks Gents - I have tried your suggestions and also replaced the air flow meter.
I will let you know the outcome after I have done another 100 miles!

 

[helmut]

Now this is interesting...Have you completed 100 miles yet?

I have exactly the same problem as you,throwing up the same o2 fault as yours.I was about to order 2 new sensors as you have done but have read the response regarding split coils.
I have just replaced 3 packs(thats all euros had in stock) and on further investigation all 6 are split to some degree or another.I changed the worst 3,which had split to such an extent that the packs themselves had rusted badly.Think I'll change the remaining 3 before the o2 sensors.

 

[pjwakefield]

Hi gents, did you solve the problems? as i have just had this light come up myself saying no sensor activity detected bank 2 sensor 1 , code p0154 ?

 

[berty987]

The pre cat sensors that sit in the exhaust manifold are designed to monitor the emissions and control the fuel / air ratio. It is possible the fault is caused by a crack in the manifold or bad seal on the gasket. Id suggest getting the emissions checked on the porsche workshop tool ,,to identify if the values are low or high and how the post cat sensors are reading. If the post cat sesnors follow the same pattern of low and high as the pre cat then you can take it that the values are genuine from the "faulty" sensor. If the post cat sensors both read similar values which are different to the pre cat ones then it looks like a sensor or possibly local connector issue. There are different types of sensor for pre and post cat so its also worth double checking the correct part was ordered and fitted.