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Audi0405
Audi0405, Technician
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Experience:  10 years in Vw and Audi Field
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audi A4 Quattro: Audi has codes P0420, P0130, p0171 and P0507

Customer Question

Audi has codes P0420, P0130, p0171 and P0507 to me it seems like it should be the upstream O2 senser. i usaualy would not care about this but after these codes went off my car is running like crap is it the o2 senser
Submitted: 2 years ago.
Category: Audi
Expert:  Audi0405 replied 2 years ago.
Welcome to Just Answer!!

Ok p0420 fault is for a faulty catalytic converter and if you dont have one this may be why the fault have been triggered but since you have a front 02 sensor fault would start by replacing the front o2 sensor first , also since the vehicle is running rough and you have a fault p0171 which is a system too lean issue i would look for broken vacuum hoses, breather hoses under the intake if no hoses are broken you may have a faulty mass air flow sensor , the p0507 fault is related to the vehicle running to lean . I hope this helps.

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Expert:  Audi0405 replied 2 years ago.
Does this help?
Customer: replied 2 years ago.
i have had the down pipe for 3 years i have never had a problem could a faulty o2 senser cause all these problems I have come to relize with audi once you throw one code you will throw 5 more and if you fix the main problem your good
Expert:  Audi0405 replied 2 years ago.
The 02 sensor can cause a lean condition also start with the 02 sensor first if the p0171 fault returns then you will need to look for a vacuum hose and broken breather hoses under the intake manifold . I hope this helps.

Please dont forget to click accept for my time and knowledge thank you !
Customer: replied 2 years ago.
forgot when this all happened i was driving and i felt like someone was pulling on the brake it kind of had a pulse. then when i stopped at the traffic light the rpms went for 1000 to just above 2000 like i had been pressing on the gas
Expert:  Audi0405 replied 2 years ago.
This sounds like a vacuum leak check for this first , there is also a check valve INSIDE the hoses under the intake manifold we have seen where this 3 way valve has a spring inside of it and will break and cause a couple of these driving issues you are having and some of these faults. I hope this helps.

Please dont forget to click accept for my time and knowledge thank you!
Expert:  Audi0405 replied 2 years ago.
Has any of this info helped??

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10 years in Vw and Audi Field