BMW may show the key symbol on the instrument cluster and car won't start. The key may have a slash, line or exclamation line on top. In some cases, you will have a key symbol and Park showing on your instrument cluster at the same time. This means that the BMW is not recognizing the key which could be due to several reasons as outlined below. If you try to push the Start button, you get this warning lamp and nothing happens. BMW won't start or turn over. The vehicle is not recognizing the key which could be due to several reasons.
If BMW yellow key warning light displays when you are driving it is because the car stopped recognizing the key in the cabin. This can be due to the key being physically removed from the car or a problem with the comfort access. If you don't have the key and turn off the ignition, you can restart your BMW by pressing Stop/Start button within 10 seconds after the car has been shut off. Even if there is no key in the cabin.
BMW will not start or turn over
Yellow key warning light on the instrument cluster
BMW PARK warning light on
Car or Instrument Cluster doesn't turn on
Key symbols come up while driving
If your BMW key fob got wet because you washed it or let it out in the rain, it can fail to communicate with your BMW. Let the BMW key fob dry for a few hours and try again. If a BMW got wet, it may stop working. Even if the key starts to work again, you shouldn't rely on it as it may stop working at any time.
Defective BMW key
Comfort access not working
Low battery voltage
Water in BMW keyfob
Local radio waves
Check Key Fob Battery
Replace the batteries in your key fob. If you have comfort access the batteries may be dead. If that is the case, your BMW will not recognize the comfort access key. Follow the instructions on this guide to learn how to replace BMW key fob batteries.
A temporary solution would be to start the car by inserting the key into the key slot. If your BMW has Start/Stop button, you will need to hold the key next to the steering column where you see a small key symbol. Some BMW models have a slot where you can insert the key for a manual start or press the key against the Stop/Start button.
Try a spare key
Try another key. There is a very good chance that the BMW key fob has failed. If you have a second key, try starting the car with it. If the car starts and runs fine with the other key, then the first key fob is defective.
Check Car Battery
Check the age of the main battery on your BMW. If the battery is over 7 years old, replace it even if you think you don't need a new battery. BMWs are very sensitive to the battery and voltage drops. A low battery can cause electrical issues including the key to not be recognized by the ignition. Follow this guide to learn how to replace BMW battery. Rember to perform battery registration as outlined in the tutorial.
Read Fault Codes
If your BMW still won't start or turn on, it is time to get a diagnostic scanner and read the codes. A generic OBD2 scanner will not help you much, but a BMW specific scanner will be able to read BMW specific codes.