A4 2002 Eng. ALT Engine warning light on

[Golfer777]

Audi have looked as this vehicle & said that it needs a new catalytic converter.
Has had an E.M.L. come on since the light has been cleared reset.
The that it came up with was:

16804: Catalyst system bank 1, efficency below threshhold
P0420 - 001 - Upper limit exceeded Mil on

The vehicle has just been Mot'd & went through fine on the emissions.
Have looked on Auto Data & it says probable cause, Catalytic converter or wiring to the HO2S2.

I take it that HO2S2 is an oxygen sensor???
(Is it the sensor behind cat. being number 2)

Any help or info greatly recieved.
Vehicle has done 165,000 miles

Many thanks
Paul

[indian jalepeno]

Hi, mine has exactly the same problem, I too have a ALT engine. Flew through its MOT but comes up with the same cel codes as yours.
Have changed the MAF (no difference), throttle body cleaned (slightly better idle - not jumping), front lambda sensor (o2 sensor) light still comes on. So my next step is to get a rear lambda (post cat) and see if that sorts it. Knowing my luck it will be the cat but my Audi Indy has said that we can get away with aftermarket ones, albeit may not last as long as OEM Audi stuff, but a damn sight cheaper unlike the lambdas where they really need to be the original ones. Front will set you back about £90, rear about £70-80

Loads of info on here about checking MAF etc
Keep us info'd..good luck!!

[RickT]

Audi have looked as this vehicle & said that it needs a new catalytic converter.
Has had an E.M.L. come on since the light has been cleared reset.
The that it came up with was:

16804: Catalyst system bank 1, efficency below threshhold
P0420 - 001 - Upper limit exceeded Mil on

The vehicle has just been Mot'd & went through fine on the emissions.
Have looked on Auto Data & it says probable cause, Catalytic converter or wiring to the HO2S2.

I take it that HO2S2 is an oxygen sensor???
(Is it the sensor behind cat. being number 2)

Any help or info greatly recieved.
Vehicle has done 165,000 miles

Many thanks
Paul


Where abouts are you?


Rick

[Golfer777]

In Southampton RickT, what you thinking?

Paul

[Golfer777]

Any ideas anyone??? :confused:

[smokey0123]

What are the CO and HC readings on your emmisions printout? if it passed the MOT I doubt it is the cat.