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[Dave C]

Hi,

After several months of no fuss motoring my emmisions light has come on again, last time is was fuel trim codes which was solved with a new MAF sensor. Now it is the dreaded Cat efficiency Codes, 0420 and 0430, this just before Xmas. 

Are these codes specific to the Pre-Cats or can they relate to the main Cats.

From an old MOT emmisions test (2007) the CO emmitted by my mig during the Natural Idle test was  0.03%  pass mark being below 0.30%.

The recent 2009 MOT emmisions test showed a rise of CO during Natural Idle, up to 0.292%   

However the Fast Idle results shows no change between the two emmisions tests.

Do these results show faulty pre or main cats?

If i went ahead with the moving of the Lamda sensors behind the main cats would the emmisions be sorted or am i potentialy looking at replacing both cats?

Many thanks

Dave

[Entwood]

Fairly well known and documented problem ... 

Solutions proposed....

1) Buy a code resetter and turn off the light when it comes on. Repeat as required.

2) Move the sensors to behind the main cats where they will read the "true" state of the exhaust, not just the "partially cleaned by the pre-cat" exhaust

3) Replace cats at great expense to have the same thing occur in the future.

I've gone for option 1) as the only times in 2 years that I've had the problem are after changing fuel to French and then back ... there's a long winded post about it somewhere ...

When I got the 3.2 I was told it is not a question of IF this problem occurs.. but WHEN ... and that seems to be true. In 2 years I've had 4 warnings, as said in pairs seperated by a few weeks. The £80 resetter has paid for itself and is IMHO the easiest solution.

[Dave C]

 Thanks for replying,

Went on long journey to family and stopped half way, when i restarted the engine the Emmisions light went out to my surprise. It stayed out until today when it reappeared with the same old codes.

I am not going to do any mods to the positioning of the Lambda sensors just yet. Will get a local trusted mechanic to put it through an MOT emmisions test, cannot see the reason to carry out mod if it will fail the emmisions test. The two differences in the MOT emmision tests i posted above have me curious.

My MOT is not due until April 2010 so have a few months to investigate the problem and to get the best solution.

If any one has any solutions out there i would be interested to hear how this was cured.

Many thanks   

[Welung666]

I did a howto recently on moving the lambda sensors, it's in the maintenance guides