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Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 22903
Experience:  BEng hons Mech engineering, in auto industry 22 years
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my audi is failing its mot due to emmissions the MAF

Customer Question

my audi is failing its mot due to emmissions the MAF has a reading and the lamba sensors are brand new ive had a digonist device on it but no luck car is audi a3 2000 1.8t can you help.
Submitted: 3 years ago.
Category: Audi
Expert:  Matt replied 3 years ago.

if there's no check engine light or other fault light on and its still faililng emissons then its very lilkely that the cataylst has failed or is coked up

You say you've replaced the exhaust but did this include the front downpipe with the cat in it?

if you haven't got a new cat on it then you could replace the cat with a new part £100 in parts plus an hours labour

but I'd reccommend trying a bottle of this stuff 1st as I've had several good results with it

Customer: replied 3 years ago.

there is engine management light and abs light on only recently both of them i have fitted a new cat at the same time as i fitted the new lamda sensors also new middle and rear exhaust i have tried the cat clean but nothin happen emmissions never moved

Expert:  Matt replied 3 years ago.

Ok when you plugged in the diagnostic device can you tell me what fault codes it pulled off?

if there were no codes then I'd suggest getting this test done by someone with the VW / Audi diagnostic tool as often the generic readers won't provide a code of the more uncommon faults
Customer: replied 3 years ago.

The codes that came up are







Expert:  Matt replied 3 years ago.

thats a lot of codes! and if they are all accurate its no wonder the car won't pass as these are all emissions system faults

P0445 = purge valve shorted out - this valve controls the vapour from the fuel tank back into the engine - it should be closed at idle , if its jammed open then you'll have a rich fuel mixture - so check that its wiring is undamaged

P0036 - O2 sensor heater issue - so either the sensor is faulty or again its a wiring fault
P0418 - secondary air system fault with relay - so the secondary air pump isn't getting any power, check its connection and measure with the engine running as it shoudl be on at idle
P0412 - secondary air system relay 'A' circuit fault - as above
P0103 - MAF signal too high - remove the MAF sensor and clean it with some electrical cleaner spray also check on the air intake
P0030 - O2 sensor Heater circuit fault - voltage too high - same advice as P0036
Expert:  Matt replied 3 years ago.

do you still need help with this?