Code P0420 - Cat or sensors?

GuardianAngel wrote:

GuardianAngel wrote: KwikFit do a free Exhaust/Cat check. Have booked one on-line. I cant post the link because the forum thinks I am spamming, so just go to the KF site and the option is obvious.

Betcha you end up needing a complete new exhaust, 4 tyres 4 shock absorbers, brake disks and pads too.

"Yes Sir we have checked your car. Now please bend over and touch your toes...." :ohmy:

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The boys on the forum for The Other Car are looking at a magic fluid called BG44K Fuel system cleaner.

It is supposed to degunk the engine, eliminate the lumpy missfire from 140,000 miles of driving, and clean the catalyst.

Only £14 on eBay, there are good reviews on the 'net: I'm going to get a can for my Jimny, although I worry that all the gunk is keeping the engine together, and it will all go into the catalyst and block it up anyway, but I've had a lumpy idle for the last 3 years, so I may take a punt.
It might just work, and clean the catalyst too.....

My list of codes from the workshop manual says for this code "Catalyst system efficiency below threshold"

However, I had a similar code came on if I drove at the same revs for some time and I cleared it and turned the light off, passed an MOT, then the following year, having cleared it a few more times throughout the year it failed the MOT and needed a new CAT to get through.

So I would take MarkyP2000's advice and take it to a friendly MOT station and ask them to put it on their emmissions machine, having turned the light out. If the emmissions are ok, carry on as normal and see what happens.

I don't think putting any cleaning liquid in the fuel will help much really.

I would also advise avoiding Supermarket petrol, especially the big one beggining with T. This kept throwing the equivalent code up on my Mrs BMW 325. The lambda's were tested and are fine, the CAT's apparently never go on those cars and are extremely expensive. It also passed an MOT with very low emmissions. So i suggested to her only buying proper petrol (the Shell 1/2 a mile from the big Supermarket beginning with T price matches them) and it has not come on since!

As a consequence, none of our cars get Supermarket petrol put in them.

As has been said above - do not go to Kwik Fit - you'll find out you need a whole new exhaust, new brake discs and pads, front and rear - despite the fact you have drums on the back, new lambda sensors and windcreen wipers.

Kirkynut

no suzuki will fail the mot on emmisions unless the co is above 3.5% or hc is above 2000ppm

GuardianAngel wrote: My list of codes from the workshop manual says for this code "Catalyst system efficiency below threshold"

However, I had a similar code came on if I drove at the same revs for some time and I cleared it and turned the light off, passed an MOT, then the following year, having cleared it a few more times throughout the year it failed the MOT and needed a new CAT to get through.

So I would take MarkyP2000's advice and take it to a friendly MOT station and ask them to put it on their emmissions machine, having turned the light out. If the emmissions are ok, carry on as normal and see what happens.

I don't think putting any cleaning liquid in the fuel will help much really.

I would also advise avoiding Supermarket petrol, especially the big one beggining with T. This kept throwing the equivalent code up on my Mrs BMW 325. The lambda's were tested and are fine, the CAT's apparently never go on those cars and are extremely expensive. It also passed an MOT with very low emmissions. So i suggested to her only buying proper petrol (the Shell 1/2 a mile from the big Supermarket beginning with T price matches them) and it has not come on since!

As a consequence, none of our cars get Supermarket petrol put in them.

As has been said above - do not go to Kwik Fit - you'll find out you need a whole new exhaust, new brake discs and pads, front and rear - despite the fact you have drums on the back, new lambda sensors and windcreen wipers.

Kirkynut

Just before I went on my trip this weekend I put in fuel from T! The light came on during my motorway run, so it was during a long run at highish revs. Interesting parallel.

I will reset the code and get it tested at KwikFit and just ignore their BS about what "needs" to be replaced.

Cheers

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Yes, a different MOT tester was telling me this recently - is this because there are no published specs for it Mark? So it has to fall back to those stats? That's what I've recently been told. A bit like the Mk1 Eunos Roadster I understand, Mazda never produced specs for that either - am I right?

With the new cat the emmisions did improve dramatically - however, I was somewhat confused by the EML not coming on and staying on, even after I cleared it, to tell me the emissions were out of range.

This could be the reason why - the range the emmissions are allowed to go to are alot higher than it was being tested to!

I have an MOT tester singing from the right song sheet now - so should be alright from now on!

Kirkynut