help

[acano]

I have dipped my toes , so to speak and purchased a cheapo cable with shareware 409us. At that small cost, it was worth having a go before I go and purchase the full vcd service.
Anyway as i had the engine management light on again thought i would scan, it came up with this code
1 Fault Found:

16804 - Catalyst System: Bank 1: Efficiency Below Threshold

P0420 - 001 - Upper Limit Exceeded
this is the 2nd time since buying the car that this code has come up 1st time i got it check at dealers. They said that nothing was the matter with it so they cleared the fault, what i want to know is, why if nothing wrong with it would it re-appear and where is the sensor that it relates to?

the car I have is an A4 2001 2lt petrol saloon any help appreciated

Tony

[bearthebruce]

the car has 2 oxgen sensors - one is before the cat and one is after the cat. the front O2 sensor is used in the control of the fuel mixture and the post cat O2 sensor is used to monitor the efficiency of the catalytic conversion. Often, when the efficiency error code is thrown, there is nothing wrong with the sensors but there can be a leak of air into the exhaust system. There are a number of possibilities.

[acano]

thanks I'll check for any leaks

[acano]

Ok so i keep getting this fault code thrown up, not really sure why, but I took my car into audi again, to get it checked. Came back that the cat is fine no holes (none they can see anyway) and they said that the sensors were fine, but on the same breath said I should maybe change the sensors to see if that will sort the problem and then maybe the cat.
seems a bit strange considering they said all was fine!

so anyway done a bit of a search and found this was wondering if anyone had used one before or even thought it might work?
any thoughts?

Tony

[saabsalltheway!]

hi check this out
http://wiki.ross-tech.com/index.php/16804/P0420/001056

that item off that site seems a brilliant idea especialy if there is a air leak and the car is running lean now and your prepared to make it leaner and melt a piston or 2
best to find the fault first
paul

[acano]

Not a good idea then!
Oh well back to square one, so if audi have checked the system and checked the sensors, and all comes up fine which they did.
What now?

[saabsalltheway!]

check all the intake system all small vac pipes breather pipes for leaks check the exhaust system from the engine all the way to the tail pipe
what fuel are you using?
have you got a after market exhaust system fitted?
check the wiring to the o2 sensors
paul

how about taking it to a mot station and asking them to do a emissions test

[acano]

ok thanks for the reply