why does my Volkswagen Golf MK7 (2015-2019) key fob not work after replacing the battery

Solution

1. Preparation

• Gather necessary tools: OBD-II scanner, multimeter, small screwdriver set, and a clean workspace.
• Ensure the vehicle is in a safe environment, with no electronic interference.

2. Inspect Battery Installation

• Open the key fob casing using a small screwdriver.
• Remove the battery and inspect for proper installation.
• Reinsert the new battery ensuring the positive (+) and negative (-) terminals are correctly aligned.

3. Test Battery Voltage

• Use a multimeter to measure the voltage of the new battery.
  • Set the multimeter to the DC voltage setting.
  • Touch the positive lead to the positive terminal of the battery and the negative lead to the negative terminal.
  • Ensure the reading is approximately 3V; replace if necessary.

4. Inspect Key Fob Circuit Board

• Visually examine the circuit board for any cracks or damage.
• Clean the contacts and circuit board with isopropyl alcohol and a soft cloth.
• Ensure all buttons are functioning mechanically by pressing them and listening for clicks.

5. Reprogram the Key Fob

• Enter the vehicle and close the doors.
• Insert the key into the ignition and turn it to the "On" position (do not start the engine).
• Press the unlock button on the key fob for approximately 5 seconds.
• Turn the ignition off and remove the key, then test the fob operation.

6. Test with OBD-II Scanner

• If the fob remains unresponsive, connect the OBD-II scanner to the vehicle's diagnostic port.
• Check for any stored fault codes related to the key fob or immobilizer system.
• Clear any codes and attempt to reprogram the fob again as necessary.