BMW Comfort Access Not Working: 12 Troubleshooting Tips And Solutions

You walk up to your BMW, grab the door handle just like always, but this time, nothing happens. Your BMW comfort access keyless entry system has suddenly stopped working. What could cause this frustrating issue, and how can you get your BMW comfort access to work again?

This complete guide will walk you through 12 of the most common troubleshooting tips and solutions to get BMW comfort access and keyless entry working again when it fails unexpectedly. We’ll cover quick DIY fixes like checking the key fob battery and resetting the system, to when professional diagnosis and BMW service is needed. Follow our step-by-step instructions below to unlock your BMW doors without the key fob, and restore the convenience of keyless driving.

What is BMW Comfort Access and How Does it Work?

BMW comfort access, also known as BMW keyless entry, is a convenience feature that allows you to unlock the doors, open the trunk, start the engine and more without taking the smart key fob out of your pocket.

Here’s a quick overview of how BMW comfort access works:

Each programmed key fob has an electronic ID code that wirelessly communicates with antennas and sensors located in your BMW’s door handles, trunk, ignition button, and control module.
When you grab the handle or touch the trunk release, the door handle antenna detects the nearby key fob. If the ID codes match, the doors unlock automatically.
To turn on the ignition, you simply need to press the Start/Stop button on the dash while the key fob is inside the vehicle. The BMW comfort access system recognizes the fob and allows the engine to start.
You can also lock the doors by touching the indentations on the exterior door handles with the key fob nearby. The door handles sense the fob and activate the locking mechanism.

This keyless access system is designed for maximum convenience, but like any advanced technology, glitches can happen causing BMW comfort access failure. Let’s look at the typical symptoms next.

Symptoms of BMW Comfort Access Not Working

When your BMW comfort access system stops functioning correctly, you’ll experience one or more of these common problems:

Door fails to unlock when you grab the door handle: Thesensors in the door handle don’t detect your key fob so nothing happens when you pull the handle.
Unable to lock doors by touching exterior door handle: Again, the door handle cannot sense your key fob nearby so the locking function doesn’t activate.
Engine won’t start or stop with the START/STOP button: The ignition button only works when your key fob is inside the vehicle, within range. If not detected, the engine won’t turn over.
Flashing orange LED light around Start/Stop button: This warning light indicates a problem with the key fob detection. Either the fob’s battery is dead or no fob is present.

Any of these issues point to a problem with your BMW comfort access that requires troubleshooting to get fixed. Now let’s look at the most common causes and solutions.

1. Check Key Fob Battery

The first thing to check when BMW comfort access stops working is the smart key battery.

A low or dead key fob battery is the number one reason BMW comfort access fails and prevents keyless entry or engine starting. The battery needs sufficient charge to broadcast the ID code to your BMW’s comfort access system.

If the battery gets too weak, the operating range will decrease and the sensors in the door handles, trunk, and ignition button won’t be able to detect the key fob signal. All comfort access functions will fail.

How to Replace Key Fob Battery

Replacing the battery in your BMW smart key fob is quick and easy:

Look for a small release button on the back or side of the fob. Press this to release the backing.
Carefully pry open the two halves of the key fob.
Remove the old battery and replace it with a new CR2032 3-volt lithium coin cell battery. Match positive/negative terminals.
Snap the key fob closed again. Resync with vehicle (see next section).
Test comfort access operation. The battery replacement should have fixed it!

Keep in mind that using a lower voltage regular alkaline or rechargeable battery may not provide enough power for the key fob circuits. A fresh CR2032 coin cell is recommended.

2. Make Sure Key Fob is Paired/Synchronized

Before comfort access functions will work, your BMW smart key must be electronically paired and synchronized with your vehicle. This is normally done automatically when programming new keys.

But sometimes after replacing the battery, the key fob loses its synchronization. Until paired again, BMW comfort access will not work even with a new battery.

Here are steps to resynchronize and reprogram your key fob:

Start by inserting the metal remote key into the door lock and turning to unlock the driver door.
Get inside the vehicle and insert the key fob into the ignition slot. (For BMWs with Start/Stop button, there is usually a slot or key symbol behind the button to insert key).
With the key fob in this position, press the Start/Stop button once without stepping on brake. Do not start engine.
All dash lights and electronics should now activate. This indicates the key fob is synchronized.
You can now remove the key and test comfort access. It should be working again!

If you still have issues, you may need to reset the system using a diagnostic scan tool that can program BMW comfort access and key fobs. Some independent shops and dealerships offer this service.

3. Check Key Fob Location and Interference

Even with adequate battery charge and proper synchronization, comfort access problems can occur if the key fob is too far from the vehicle or experiencing signal interference.

Here are some tips for maximizing BMW comfort access range and avoiding interference:

Don’t leave the key fob in the trunk or rear cargo area. This may be too far from the door handles and ignition for detection. Keep it in a front pocket whenever possible.
Avoid placing the fob near other electronic devices like phones that can cause signal interference.
Check for any aftermarket electronic devices installed that may jam key fob frequencies. Remote car starters, for example, can sometimes disable comfort access.
Eliminate sources of electrostatic buildup on yourself which can temporarily block the key fob signal until discharged.
Make sure you are not near other vehicles with comfort access systems that could cross-communicate and disable your fob signal.
Extreme hot or cold temperatures can reduce operating range. Avoid leaving key fob in extreme environments.

With these precautions, you can maximize the wireless operating range and help avoid comfort access failures related to key fob position and interference.

4. Reset BMW Comfort Access System

If your comfort access problems persist after checking the basics above, try resetting and reinitializing the whole BMW comfort access system.

On some BMW models, this can be done by an owner through a specific sequence of steps to reset the CAS control module and re-synchronize components.

Here is one potential reset procedure, but steps can vary by model year so look up the correct reset sequence for your BMW:

With foot NOT on brake, press Start/Stop button twice to power vehicle electronics on (don’t start engine).
Open and close driver door.
Press Start/Stop button again twice to turn electronics off.
Wait 15 minutes without opening doors.
Restart vehicle. Comfort access should now be reset and working.

For some BMWs, you must use a professional grade diagnostic scan tool to access the various control modules and perform a complete CAS system reset. Independent shops or dealerships can often provide this service at a reasonable hourly rate.

5. Replace Faulty Door Handle or Antenna

The electronic components inside your BMW’s door handles are essential for comfort access operation.

The outer door handle contains an antenna that wirelessly communicates with your key fob. If this antenna is damaged or defective, it can’t detect the key signal and comfort access won’t work.

Door handle issues tend to affect one door rather than all doors at once. So pay attention to which door is not unlocking properly or showing other problems. This indicates the faulty handle to replace.

Follow these steps to replace a BMW door handle with integrated comfort access antenna:

Remove inner door panel covering the handle mounting bolts (tutorial videos can be found online for your BMW model’s door panel removal process).
Remove the mounting bolts from the exterior door handle mechanism.
Unplug any electrical connectors going to the door handle.
Install the new BMW replacement door handle and reconnect connectors. Ensure proper water sealing.
Reinstall door panel and test operation. The new handle should restore comfort access functionality.

Be extremely careful not to damage any small control modules or wiring when removing the door panel to access the handle. And make sure to get the correct replacement part number for your BMW model and year.

6. Comfort Access Control Module Failure

The CAS or comfort access system control module is essentially the computer brain that makes your BMW’s keyless entry function.

It’s responsible for wireless communication with the key fob to validate the ID code and authorize doors to unlock or the engine to start.

If this module has an internal failure, it can cause widespread comfort access problems. All doors and ignition may be affected rather than an isolated door issue.

Warning signs of CAS failure:

Key fob seems to randomly work/not work in all doors and ignition. Intermittent problems.
BMW comfort access problems began after a recent vehicle impact or accident that could have damaged modules.
No problems found in battery, key fob, door handles, or resets/reprogramming.
Diagnostic trouble codes related to CAS module or internal errors.

In most cases, the CAS module will need professional diagnosis and replacement to restore normal comfort access operation if faulty. Unless you have advanced electrical skills, this repair is best left to a knowledgeable BMW technician.

7. Low Vehicle Battery Voltage

For BMW comfort access to work properly, your vehicle must have sufficient battery charge.

If the starter battery is weak or dead due to age, a parasitic drain, or leaving interior lights on, the comfort access system may act erratically or fail completely.

Why? The CAS module and certain antenna circuits require a minimum voltage to function normally.

Signs of low vehicle battery causing comfort access problems:

Lights dimming whenever you try to start the engine.
Battery tester shows very low CCA charge level.
Other electrical issues like flickering lights.
Jumping the battery immediately restores comfort access operation.

To correct this issue, use jump start cables to jump the battery from another vehicle or a portable jump pack. Let the vehicle charge for at least 30 minutes before testing comfort access.

Or fully recharge the battery using a trickle charger if convenient. Top off the charge to 12.4-12.6 volts if possible.

This should restore normal electrical system voltage and allow comfort access to work again, at least temporarily until the weak battery is replaced.

8. Check for Fault Codes

Your BMW comfort access system constantly monitors itself for problems and stores diagnostic trouble codes (DTCs) whenever it detects a malfunction.

Accessing and reading these BMW fault codes can provide helpful clues to pinpoint the source of comfort access failures.

However, most owners will need a professional-grade OBD2 diagnostic scan tool to access BMW comfort access fault codes.

Independent shops and dealerships have these tools to read codes set by the CAS module, door handles, key fob, body controller and other components tied to the comfort access system.

If you notice your BMW comfort access failing, it’s smart to ask the repair shop to scan all modules for related fault codes before they begin troubleshooting. The fault codes will guide them right to the issue.

9. Unlock Manually with Metal Key

If you are stuck unable to start or drive your BMW because comfort access is completely disabled, all is not lost.

You can still manually unlock and start your car by utilizing the metal remote key integrated inside the key fob.

Insert this traditional metal key into each door to manually unlock. Then insert the key into the ignition slot and turn to start the engine as you would pre-comfort access vehicles. No need to call a tow truck!

Once inside your BMW, you can further troubleshoot the comfort access failure using the tips in this article and hopefully restore normal keyless operation.

But this metal key backdoor ensures you can always get in your vehicle and enables you to safely get to a repair shop for diagnosis. Just be careful not to lose that valuable metal key!

10. Professional BMW Diagnosis and Repair

If you have followed all troubleshooting tips suggested here but your BMW comfort access still fails to work properly, it’s time to enlist professional help at a BMW service center.

Certified BMW technicians have the software, tools, and experience to properly diagnose comfort access problems and make necessary repairs.

Below are some specific ways a mechanic can help:

Pinpoint issues through diagnostic OBD2 scans for fault codes.
Confirm CAS module malfunction and replace if necessary.
Remove and replace a bad door handle antenna or mechanism.
Reprogram and synchronize your key fobs if they lost pairing.
Flash update vehicle software, which may include updates to the comfort access system.

While an independent mechanic familiar with BMW electrical systems can also be helpful, the dealer may provide the most direct fix since they have direct access to BMW repair procedures and software.

Just be prepared for potentially higher hourly labor rates at the dealer. Get a written estimate before approving any repairs.

11. Evaluate Aftermarket Accessories

Do you happen to have any new aftermarket electronics or accessories installed right before noticing comfort access issues?

Non-BMW accessories like remote car starters, security systems, GPS trackers, or Bluetooth devices can sometimes interfere with comfort access signals.

Any device that broadcasts its own wireless signals in your car’s cabin or connects to the vehicle wiring has the potential for causing key fob communication glitches.

Evaluate and uninstall recently added devices one at a time to test if comfort access improves. You may need to relocate the accessory antenna farther from your key fob.

Also ensure any hardwired electronics were properly installed by an experienced installer and not affecting other systems. Get them checked or removed if comfort access problems appeared after they were added.

12. Comfort Access Software Updates

Over the lifetime of a BMW vehicle, the automaker periodically releases software and firmware updates for the various electronic control units.

These updates add new features, enhance security, fix bugs, and improve integration between modules like those controlling comfort access.

If your BMW comfort access seems glitchy or fails randomly without clear mechanical cause, an outdated comfort access software version could be the issue.

Ask your BMW service center to check for any available software updates that may optimize comfort access operation. They can download and install the latest software release as part of troubleshooting comfort access problems.

Get Your BMW Comfort Access Working Again!

In summary, common causes for BMW comfort access failure include a dead key fob battery, loss of key synchronization, low vehicle battery voltage, faulty door handle antennas, bad control module, and software bugs.

Follow the 12 troubleshooting tips shown here to restore your BMW’s convenient keyless entry and ignition access.

With simple fixes like replacing the battery or reprogramming your key, you may get comfort access working again quickly without the cost of repairs.

But if problems persist, don’t hesitate to use a professional BMW technician who can diagnose deeper issues with codes and software.

Dealers and independent shops want to get your comfort access fully operational so you can enjoy keyless convenience again!