how to fix the keyless entry system on BMW 3 Series G20/G21 (2019-2024)?

BMW 3 Series G20/G21 (2019-2024)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

3 min read

535 words

Problem Statement

The keyless entry system on a BMW 3 Series G20/G21 (2019-2024) is malfunctioning, preventing the owner from locking or unlocking the doors remotely.

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical components to avoid shorts and electrical shocks.

Symptoms

•Key fob not responding when attempting to unlock or lock the vehicle
•"Key not detected" warning on the dashboard
•Inability to start the engine using the keyless start feature
•Battery low warning for the key fob displayed on the dashboard
•Manual unlocking of doors required, indicating a failure in the system

Diagnostic Steps

1
Check the battery status of the key fob using a multimeter.
2
Inspect the key fob for physical damage or wear.
3
Attempt to reprogram the key fob using the vehicle's onboard systems.
4
Verify the vehicle's central locking system by testing the manual lock/unlock switch.
5
Scan the vehicle’s OBD-II system for any fault codes related to the keyless entry system.
6
Inspect the vehicle’s antenna and receiver for damage or loose connections.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Multimeter
•Screwdriver set
•Socket set
•Torque wrench

Parts Required

•CR2032 battery (for key fob)

Related Faults

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Symptoms

•Key fob not responding when attempting to unlock or lock the vehicle

•"Key not detected" warning on the dashboard

•Inability to start the engine using the keyless start feature

•Battery low warning for the key fob displayed on the dashboard

•Manual unlocking of doors required, indicating a failure in the system

Diagnostic Steps

1
Check the battery status of the key fob using a multimeter.
2
Inspect the key fob for physical damage or wear.
3
Attempt to reprogram the key fob using the vehicle's onboard systems.
4
Verify the vehicle's central locking system by testing the manual lock/unlock switch.
5
Scan the vehicle’s OBD-II system for any fault codes related to the keyless entry system.
6
Inspect the vehicle’s antenna and receiver for damage or loose connections.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the vehicle battery to prevent any electrical shorts during the repair.

Tools Required:

OBD-II scanner
Multimeter
Screwdriver set
Socket set
Torque wrench

2. Key Fob Battery Replacement

Open the key fob using a small flat screwdriver to release the tabs.
Remove the old battery and replace it with a new CR2032 battery, ensuring the orientation is correct.
Snap the key fob back together securely.

3. Reprogram Key Fob

With the battery reconnected, sit in the driver’s seat with the key fob.
Insert the key fob into the ignition slot (if applicable) or press the start button without pressing the brake pedal.
Follow the vehicle's manual instructions for reprogramming the key fob, usually involving a sequence of button presses or turning the ignition on and off.

4. Inspect and Repair Central Locking System

Remove the door panel (if needed) to access the locking mechanism.
- Unscrew any visible screws and gently pry off the panel without damaging clips.
Check for any loose or damaged wiring connected to the locking mechanism.
Tighten any loose connections and replace any damaged wiring.
Reassemble the door panel and test the central locking system.