What to Do When the Car Key Can't Unlock the Door?

[CassandraLee]

The methods to handle a car key that can't unlock the door are: 1. Replace the battery; 2. Use the mechanical key to unlock the door; 3. Inspect and repair the sensor module. The steps to replace the car key battery are: 1. Remove the mechanical key; 2. Insert a flat-head screwdriver into the bottom 'open' position and pry up and down; 3. Once a gap appears, use the screwdriver to pry open the key along the gap; 4. Remove the old battery and replace it with a new one. The reasons why a car key can't unlock the door include: 1. Insufficient battery power in the key; 2. The car battery is dead and cannot detect the key; 3. Issues with the key fob or sensor module.