Fault codes p0420 and p0430 GTS

[skippiemcgee]

Hi all,

I'm 4 months into my granturismo GTS ownership and still loving the look and sound from her. It's a Fantastic place to sit and I'm still mesmerised at how beautiful a Car she is.

However I've had an intermittent warning light come on which a local specialist looked at and reset for me, he gave me some injector cleaner and advised me to only use shell quality fuel. He said it my just go away.

The codes are p0420 and p0430 which comes up as "catalyst system efficiency below threshold".

I bought an OBD reader and have reset this code a few times myself, but clearly there's an issue here.

A local garage originally said both cats needed replacing, which was going to cost an arm and a leg.

However the specialist said the lambda sensors might have gone, not cheap but somewhat cheaper than the cat replacement.


Does anyone have any experience or advise to give me.

Thanks in advance.


Skippie.

 

[conaero]

The cats do break up I know Contigo had this and his cracked wide open.

The other obvious one is the Llambdas, try swapping them from one side to another and see if the fault follows.

 

[CatmanV2]

Cats, lambdas or possibly secondary air flow?


Pull the lambdas and stuff a borescope up into the cats to check they are not breaking up.
They can be replaced with sport cats for rather less than the OEM ones I understand.

If the cats look fine, then lambdas would be my next stop.

Who is your specialist?

C

 

[voicey]

First port of call is to check if the cats are OEM or not - I've seen plenty with aftermarket cats which will throw this code. If they aren't OEM then I have a way of sorting it out for cheap money.

If the cats are OEM then you need to try and establish if the cats are gone or if it is a sensor issue. Seeing you have it on both sides I doubt it is a sensor issue but you need to be looking at the downstream sensors.

To help you diagnose, these codes are thrown when the downstream lambda starts to mirror the upstream lambda. The upstream should be switching as the mixture alternates between rich and lean but the downstream should be steady as the cat stores and releases oxygen.

This is not going to go away with injector cleaner and V-Power and I can't believe a Maserati specialist would suggest such a thing - this is a basic fundamental of modern engine control.

 

[CatmanV2]

Cheers Voicey!

C

 

[skippiemcgee]

Thanks all,

Voicey, how do I establish if they are aftermarket, would a photo of the underside do it, if so where are they?

Again thanks for the advice in advance.


Nick.

 

[voicey]

Yep - take a photo of the exhausts under the front of the car and post it up.

 

[Contigo]

Standard


Larini Sports Cats

 

[skippiemcgee]

Ok will do.

I'm 95% sure they are standard, but I'll confirm.

It will be next week as I'm away until Saturday.


Best regards.

 

[skippiemcgee]

Standard by the looks of it.


Nick

 

[voicey]

Yes they look standard. My next port of call would be to pop a 'scope into the cat to have a look at the internals. I would also want to graph the four readings from the lambdas to see what is being reported.

However, given you're DIYing here and the low cost of Lambda sensors it may be worth while chucking a pair of downstream sensors on to see if that is the issue.

 

[skippiemcgee]

Hi Voicey,

Thanks for the reply.

I'm not into mechanics, IT yes, engines no, so self fixing is not an option.

Also, i'm not really local to you, So getting the car to you won't be simple but not impossible.

To do the scoping, how long would you need the car and what would the cost be. Also to look at the readings?

Same question for the Lambda sensors.

If you'd prefer to message me then please feel free.


Nick.

 

[voicey]

No need to come all the way to Kent - take it to Migliore Cars in Bromsgrove, they know what they're doing.