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[Proz]

Hi
Just passed the mot but im having the cat code P0420 as you may be aware ... Failed the first fast idle but passed the second one no problem   ... i took her for a fast blast before going in ...

Results are

Fast Idle
Eng Speed .... 2750-3250 rpm
CO ...........0.603% Fail
HC............45ppm Pass
Lambda ....1.028 Pass

Second Fast Idle
CO ......0.211% Pass
HC ......12ppm Pass
Lambda .....1.013 Pass

Natural Idle
CO ..... 0.496% Pass

So she did pass and i should really learn to ignore this code and light but it pi**** me off  :-/.
I also understand it would pass the second test cause it would be nice and hot , so is this purely a cheap crap cat that was put on by Vx six months or so ago ..... now that its passed the Mot i cant go back and rant at Vx for fitting crap where i could have if it had failed .
 

[Proz]

 

[damon80]

I thought you had done the mod that Albatros suggested - i.e. relocating the sensors behing the main cat as oppose to the pre-cat?  Or did I just dream that...?    

[damon80]

Incidentally, when I was thumbing through the service history print-outs of my Miggy (ex plod), 3 months before I purchased it there is a job listed as "Investigate/Rectify Emissions Check Light".

Anyway, they spend almost £1,000 sorting it    I would assume that's the cost for 2 new cats (double-skinned on plod-mobiles I believe?)

Anyway, a couple of months after I bought it, the emissions light came back on, with - guess what - codes 0420 and 0430...

It had done almost 80k miles before the fault originally occurred, and then 30k when it occurred to me.

Now, I've got a couple of theories here... could it be:

a) new cats aren't anywhere near as good quality as the originals? or,
b) the o2 sensors get goosed over time??

The mind boggles...

[jb]

a common fault where the pre cat efficency dies giving the eml light but main cat fine and mot fine.failed first test usually due to the engine not hot enough-good 10 miles at 4000 rpm soon get them hot prior to mot....

[Proz]

I thought you had done the mod that Albatros suggested - i.e. relocating the sensors behing the main cat as oppose to the pre-cat?  Or did I just dream that...?    

I only have one main cat .... one O2 sensor before it and one after it as the fix suggests but didnt help .... im going to just take a chance and try and get a good quality cat sometime