Please help URgently!!!

Hello, I have 2001 S40 (1.6liter Petrol), with 283000KM mileage. The check engine light came on. When I checked it with OBDII reader,
the complete error code and message is:
Fault Code:[P0420], Catalyst System Efficiency Below Threshold (Bank 1).

Can someone please guide me? Is it O2 sensor or catalytic converter?
I tried to search but looks like there are 2 catalytic converters in S40 2001?? and also the O2 sensors are more than one!!

I am in Finland, and it is really really expensive to go to workshops... and also the parts are very expensive. Therefore I plan to buy them online and try to replace myself.

NOTE: The annual inspection of my car is in the beginning of March

Many thanks and Regards

 

 

Buy this and never worry about the cat conv again. Remove the bottom O2 sensor, screw this into the hole, then screw the bottom O2 sensor into the back of this:

Oxygen Sensor Spacer (CEL Boss)

 

Many thanks mate
I'm looking into it now. Task 1 i.e. changing the engine oil & filter and air filter are successfully done

 

Mate! but will cause any troubles when I go for the yearly inspection? Because the yearly inspection is due in the beginning of March. And they check all the emissions values.
PS: if this spacer will only turn off the warning light! (That can also be done with OBDII reader), But I'm worried if this will give some bad values when the inpection guys check it or not?
Cheers

 

Yea, forgot about the MOT. It's probably against the rules there. The piece I suggested is merely a spacer that moves the bottom O2 sensor away from the exhaust stream. This only affects the check engine light. The cat convertor works as it normally does. The bottom O2 sensor's only job is to turn on the check engine light. It does not affect emissions at all. The top O2 sensor is the one used for adjusting fuel trim.

First, if you have never changed the bottom O2 sensor in 283,000 km then it is past time. O2 sensors are good for about 160,000 km. Since the check engine light is triggered by the bottom O2 sensor it needs to be working correctly. Second, before your MOT, erase the trouble code. When my 2001 S40 started getting this code it would take a week of driving before the code returned. I would try all this before replacing an expensive cat convertor. JMHO. Tell us how it goes?

 

well, when i bought the car the mileage was already 273000km. i dnt know did previous owner changed the sensors or not. So if I'v understood correctly!! this Error code does not affect the emissions etc. So if I just remove the Check Engine Light and go for the Inspection (when the light is off), there wont be any problem. Right? Because if that's the case, I would do this right away and go for the inspection as soon as possible

Many thanks for replies

 

When I reset my code it takes about 400 miles to return.

 

if i reset the code, can the insection (MOT) guy check or come to know that I turned off the warning code? Also will there be any emissions difference?

 

I'm not 100% sure on this but there are 4 or 5 emissions checks run during a test. Usually if the car passes 3 or 4 of them the car passes, even if 1 or 2 are not "ready".

 

This is a great post, it needs a BUMP to the top.

I wanted to add that in TN if your car is a 1975 or older.... no inspection needed. If the car has an OBD2 plug that is what they use. They do not sniff the tail pipe. They only look at the data. Which is what got VW in trouble. I say, "trust the data, but verify."


And just cause the light is OUT, does not mean you are clear. The test and the readers will report pending codes. So it depends on the testing equipment and method and laws as to whether "you're" clearing of the CEL will allow a pass.

But this is my last code, so I will try all suggestions.


Good Luck to all.