how to fix my BMW 3 Series E90/E91 if the key fob isn't working properly?

Solution

1. Preparation

• Gather tools: OBD-II scanner, small screwdriver set, multimeter, and replacement battery (CR2032 or as specified by the vehicle).
• Ensure the vehicle is in a secure location and the engine is off.
• Disconnect the battery if necessary for safety.

2. Key Fob Battery Replacement

• Sub-step 1: Open the key fob using a small screwdriver to carefully pry apart the two halves without damaging the casing.
• Sub-step 2: Remove the old battery and note the orientation (positive and negative sides).
• Sub-step 3: Insert the new battery in the same orientation and ensure it is seated properly.
• Sub-step 4: Reassemble the key fob and ensure it clicks securely back into place.

3. Reprogramming the Key Fob

• Sub-step 1: Sit in the driver’s seat with all doors closed.
• Sub-step 2: Insert the key fob into the ignition and turn it to the "On" position without starting the engine.
• Sub-step 3: Press the unlock button on the key fob for 10 seconds while in the "On" position.
• Sub-step 4: Turn the ignition off and remove the key fob, then test the key fob functionality.

4. Checking for Interference

• Sub-step 1: Move the vehicle to a different location away from other vehicles or electronic devices.
• Sub-step 2: Test the key fob again to determine if the range has improved.