Audi Repair: Radio off and Engine light on, mixture problem, vacuum problem

Question
QUESTION: I have Audi A4 2002 1.8t.My radio dont work for some reason.No light at all.I check all my fuses in fuses box but all looks oky.Also engine light is on with code P0171.I found one of check valve bad next to MAF sensor.Also my brake light indicator blicking...

ANSWER: The radio has a fuse at the back of it, I would check that first.  The code P0171 is a mixture problem on one bank, so I would check all the vacuum lines etc on that side of the engine.  The brake indicator blinking could be low brake fluid, or low brake linings.  WHat color is the blinking light?  Let me know,  Jan

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QUESTION: Light is RED color and dont blink all the time. Maybe for 10sec and after that all looks oky.Also Brakes are new.I think is low fluid too.I m more concered about engine light and one guy from autozone check my car and told me that i need to change my 02 sensor (car has 98.000k).BIG Thank you for your help....I m going to check all my hoses and see if any has some leak....

Answer
If the light is red, then it is a serious warning, and may well be brake fluid level.  The check engine light is giving a mixture error, but not an O2 sensor error, so this may be an O2 sesnor not giving the right output, but could also be a vacuum problem on that side of the engine.  Let me know,  Jan