Experiencing issues with your 2009 Mitsubishi Lancer Key Fob can be frustrating. Imagine pressing the buttons to lock or unlock your car, only to be met with silence and no response from your vehicle. You’ve tried the spare key, replaced the batteries, and still, nothing seems to work except for starting the engine. If this scenario sounds familiar, you’re not alone. Many 2009 Mitsubishi Lancer owners encounter problems with their key fobs, and understanding the potential causes and solutions is crucial.
One common symptom is that while the key fob LED might blink when you press the buttons, the car doors remain stubbornly locked or unlocked. You might even have run a scan tool and received a DTC (Diagnostic Trouble Code) like B1A08, pointing towards a “Keyless (Freehand advanced security transmitter) key 1 fail.” This error code, as indicated in the Mitsubishi Lancer service manual, often relates to a synchronization issue between your key fob and your car’s KOS-ECU (Keyless Operation System-Electronic Control Unit).
According to the service manual, DTC B1A08 is triggered when the KOS-ECU detects a significant discrepancy in the rolling code from the key fob. Rolling codes are a security feature designed to prevent replay attacks, where the code transmitted by your key fob is intercepted and reused by thieves. If the rolling code in your key fob gets out of sync with the KOS-ECU, the system may interpret it as an invalid signal, hence the error and the non-responsive buttons.
The service manual outlines a straightforward troubleshooting process to address this issue, primarily focused on resynchronizing the rolling code. Here’s a step-by-step guide inspired by the official procedure:
Step 1: Rolling Code Synchronization
The first step is to attempt to resynchronize the rolling code between your 2009 Mitsubishi Lancer key fob and the KOS-ECU. This process is relatively simple and can often resolve the issue.
- Erase the DTC: If you have a scan tool, use it to clear the B1A08 diagnostic trouble code from your car’s system. This step ensures that we are starting fresh and can verify if the issue is resolved.
- Turn Ignition ON: Insert your key into the ignition and turn it to the “ON” position. Do not start the engine; simply turn the ignition to the point where the dashboard lights illuminate.
- Press Key Fob Button: Take the key fob that is experiencing issues and press either the “lock” or “unlock” button at least once. This action is intended to synchronize the rolling code between the key fob and the KOS-ECU.
- Check for DTC: After performing the synchronization steps, use your scan tool again to check if the DTC B1A08 has reappeared.
- If the DTC is NOT set (NO): Congratulations! The synchronization process was successful, and the diagnosis is complete. Your key fob should now be working correctly.
- If the DTC IS set (YES): Proceed to Step 2.
Step 2: Key Fob Replacement
If synchronization alone doesn’t resolve the problem, the next step suggested by the service manual involves replacing the key fob itself. It’s possible that the key fob transmitter is faulty.
- Erase the DTC: As before, use a scan tool to erase the B1A08 DTC.
- Turn Ignition ON: Turn the ignition switch to the “ON” position.
- Check for DTC: After turning the ignition ON, immediately check if the DTC B1A08 returns.
- If the DTC is NOT set (NO): The diagnosis is complete after key fob replacement. You will need to register the new key ID and keyless operation key ID to your vehicle. Refer to your Mitsubishi Lancer service manual for the specific procedure on key registration.
- If the DTC IS set (YES): If the DTC persists even after replacing the key fob, the issue might lie with the KOS-ECU itself. Proceed to Step 3.
Step 3: KOS-ECU Replacement
If neither synchronization nor key fob replacement resolves the DTC B1A08 and the key fob button issue, the service manual points to a potential problem with the KOS-ECU.
- Replace KOS-ECU: The final step recommended is to replace the KOS-ECU. This is a more complex procedure that may require professional assistance. After replacement, you will also need to register the ID codes. Consult your service manual for detailed instructions on KOS-ECU replacement and ID code registration.
Clearing the DTC: Battery Disconnection and Scan Tools
The original post also raises a common question: “How can I erase that DTC to try synchronize, disconnecting the car battery???”
Disconnecting the car battery can sometimes clear DTCs, as it resets some electronic modules. However, it’s not a guaranteed method and is generally not the recommended way to clear diagnostic trouble codes in modern vehicles. A proper scan tool is the most reliable and recommended method for erasing DTCs.
While battery disconnection might clear some codes temporarily, it can also have unintended consequences, such as:
- Loss of volatile memory: Some vehicle systems rely on volatile memory that is powered by the battery. Disconnecting the battery can erase learned settings or require certain systems to be relearned.
- Potential for electrical issues: Improper battery disconnection or reconnection can sometimes cause electrical spikes or other issues.
Therefore, using a scan tool is always the preferred and safer method for erasing DTCs. Scan tools provide a controlled and reliable way to communicate with your car’s computer and clear specific error codes. Many affordable OBD-II scan tools are available for DIY use, or you can have a mechanic or auto parts store clear the codes for you.
Conclusion
If your 2009 Mitsubishi Lancer key fob buttons are not working and you are seeing a DTC B1A08, the issue is likely related to a rolling code synchronization problem. Following the troubleshooting steps outlined in the service manual, starting with synchronization, then key fob replacement, and potentially KOS-ECU replacement, should help you diagnose and resolve the problem. While battery disconnection is sometimes suggested as a DIY fix, using a scan tool to clear DTCs and properly diagnose the issue is always recommended for a reliable and safe solution. If you are uncomfortable performing these steps yourself, it is always best to consult a qualified automotive technician for professional diagnosis and repair of your 2009 Mitsubishi Lancer key fob issues.
