BMW 325i: Check brakel light sensor light on

Question edited for clarity. I doubt your BMW is a 125i.

These type of faults need an auto electrician with a pro grade scan tool computer and access to factory data.

https://www.google.com/search?q=2013+BMW+325i+M+Sport%2C+801C20+ZGM.+Central+Faulty+Memory.2-D36D54SIGNEL+3-4809AB

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have code read most auto stores offer this service for free the code will assist you on how to repair or service vehicle the computer is advising something is wrong you will need to fix it first --you can reset the computer everyday but if fix is not done it will come back each time

All I know is that it is a 9 year old BMW. Probably has a little over 100k miles on it, right?
I would give better than 50/50 odds that a check engine light is telling you that your oxygen sensors are approaching the end of their service and are getting slow to respond. If you read the codes (which many auto parts stores will do for free) and the code says 'Catalyst efficiency low', the problem is old oxygen sensors.
You can replace oxygen sensors yourself if you have ramps to raise the car up.

the warning light is controlled by a temperature sensor,maybe this sensor is faulty & needs to be replaced.....hope this helps.....cheers

Horns? Phantom Code? BS. You may need to have another shop that specializes in BMW to check it out.

Code PO340 "Camshaft Position Sensor Circuit Malfunction". Now that does not mean that if you simply replace the sensor your problem will be solved. It can be simply loose, cut, or corroded wiring. It can also be something entirely different. This is where diagnostic skills come in.

you dont need to take the door off just the casing u need a workshop manual it will aways come in handy

your brake pads have a small sensor built in and when they contact the rotor it competes the curcuit and the light comes on your pads are worn out i suggest replacment soon or run the risk of needing new rotors

many reasons for this. A bad relay can do it, or a wheel speed sensor can to. Also the relay may be at fault. You can have the codes checked for free at any Auto Zone and they will tell you what part is bad

best thing to do is have it scaned at a garage or dealer, theres a problem maybe a sensor. when they scan it they will be able to tell you what the problem is and how bad the problem is. good luck, also auto zone parts store scans for free.