Are you experiencing issues with your Mitsubishi Lancer Key Fob? It can be frustrating when your key fob suddenly stops working, leaving you unable to lock, unlock, or remotely start your vehicle. This guide will walk you through troubleshooting steps, focusing on the common problem of a malfunctioning Mitsubishi Lancer key fob. We’ll explore potential causes, diagnostic procedures, and solutions to get your key fob back in working order.
Understanding the Problem: Key Fob Buttons Not Responding
Many Mitsubishi Lancer owners encounter a situation where the buttons on their key fob become unresponsive. You might press the lock or unlock button, but nothing happens. Common symptoms include:
- Buttons not working: Pressing lock, unlock, or panic buttons yields no response from the car.
- Car starts normally: Despite the button issue, the key can still start the engine when inserted into the ignition.
- Key LED blinks: The LED indicator on the key fob illuminates when buttons are pressed, suggesting the key itself is attempting to transmit a signal.
- Spare key also fails: Testing with a spare key fob produces the same unresponsive behavior.
- New batteries don’t fix it: Replacing the key fob batteries with fresh ones doesn’t resolve the problem.
If these symptoms sound familiar, your Mitsubishi Lancer key fob might be experiencing a synchronization issue or another underlying problem.
Diagnosing the Issue: DTC B1A08 – Keyless System Malfunction
A diagnostic scan tool can provide valuable insights into the problem. A common Diagnostic Trouble Code (DTC) associated with key fob issues in Mitsubishi Lancers is B1A08, which stands for “Keyless (Freehand advanced security transmitter) key 1 fail”.
According to the Mitsubishi service manual, DTC B1A08 indicates:
“If KOS-ECU receives wrong signal (out of synchronization of a rolling code) from the keyless operation key, KOS-ECU memorizes DTC B1A08. … If the difference between the rolling code for the keyless operation key 1 (the first keyless operation key registered with KOS-ECU) and that memorized by KOS-ECU is large, it is judged as abnormal.”
This technical description points to a rolling code synchronization problem. Modern key fobs use rolling codes – constantly changing security codes – to prevent theft. If the rolling code in your key fob gets out of sync with the car’s KOS-ECU (Keyless Operation System-Electronic Control Unit), communication breaks down, and the buttons stop working.
Step-by-Step Troubleshooting and Solutions
The Mitsubishi service manual outlines a clear procedure to address DTC B1A08 and key fob unresponsiveness. Here’s a breakdown of the steps you can take:
Step 1: Rolling Code Synchronization
The first and simplest step is to attempt to resynchronize the rolling codes between your key fob and the KOS-ECU.
- Erase the DTC: Use a scan tool to clear the B1A08 DTC from the vehicle’s memory. If you don’t have a scan tool, some basic OBD-II scanners are affordable and can read and clear codes.
- Turn Ignition ON: Turn the ignition switch from the LOCK (OFF) position to the ON position. Do not start the engine, just turn the key to the position where the dashboard lights up.
- Press Key Fob Button: Press either the lock or unlock button on the problematic Mitsubishi Lancer key fob at least once. This action attempts to synchronize the rolling codes.
- Check for DTC Reset: Use the scan tool again to check if the B1A08 DTC has returned.
Outcome of Step 1:
- NO (DTC is not set): Congratulations! The synchronization process was successful. Your key fob should now be working correctly. The diagnosis is complete.
- YES (DTC is set): Proceed to Step 2.
Step 2: Key Fob Replacement
If synchronization doesn’t resolve the issue, the next step is to test with a new key fob.
- Erase the DTC: Clear the B1A08 DTC again using a scan tool.
- Turn Ignition ON: Turn the ignition switch to the ON position (dashboard lights on, engine off).
- Replace Key Fob and Check DTC: Replace the original Mitsubishi Lancer key fob with a new, unprogrammed key fob. You will need to purchase a new key fob compatible with your Mitsubishi Lancer. After replacing the key, check if the B1A08 DTC returns using the scan tool.
Important: A new key fob will likely need to be programmed to your vehicle to function fully, including starting the engine in some cases. However, for this troubleshooting step, we are primarily checking if a new key fob can communicate with the KOS-ECU and resolve the B1A08 error.
Outcome of Step 2:
- NO (DTC is not set): The new key fob has resolved the issue. The original key fob is likely faulty and needs to be replaced and programmed. You will need to register the new key ID and keyless operation key ID to fully integrate the new key with your vehicle. Consult your Mitsubishi Lancer owner’s manual or a qualified technician for key programming procedures. The diagnosis is complete.
- YES (DTC is set): If the DTC persists even with a new key fob, the problem likely lies within the vehicle’s KOS-ECU itself. Proceed to Step 3.
Step 3: KOS-ECU Replacement
If neither synchronization nor a new key fob resolves the B1A08 DTC, the KOS-ECU may be faulty and require replacement.
- Replace KOS-ECU: Replace the KOS-ECU with a new unit. This is a more complex procedure and typically requires professional expertise. KOS-ECUs are specific to vehicle models and may need to be programmed to your car’s VIN (Vehicle Identification Number).
- Register ID Codes: After replacing the KOS-ECU, you will need to register the ID codes for your key fobs with the new KOS-ECU. This programming step is crucial for the key fobs to communicate with the new ECU.
- Check for DTC Reset: After KOS-ECU replacement and ID registration, check if the B1A08 DTC is still present using a scan tool.
Outcome of Step 3:
- NO (DTC is not set): Replacing the KOS-ECU has resolved the issue. The diagnosis is complete. Your new key fob and potentially your original key fob (after reprogramming) should now function correctly.
- YES (DTC is set): If the DTC persists even after KOS-ECU replacement, there may be a more complex underlying electrical issue in your vehicle’s keyless entry system that requires further professional diagnosis.
Addressing Battery Disconnection and DTC Erasing
The original user asked about erasing the DTC by disconnecting the car battery. While disconnecting the battery can sometimes reset electronic modules, it’s not a reliable or recommended method for erasing DTCs related to the keyless entry system and synchronizing key fobs in modern vehicles like the Mitsubishi Lancer.
Using a Scan Tool is the Correct Approach:
A scan tool is designed to communicate with the vehicle’s computer systems and specifically clear DTCs. This ensures that the error code is properly erased and allows you to accurately test if the synchronization or repair steps have been successful.
Battery Disconnection Drawbacks:
- Unreliable DTC Clearing: Battery disconnection may not consistently clear all DTCs, especially those stored in non-volatile memory.
- Potential for Other Issues: Abruptly disconnecting the battery can sometimes cause other electronic issues or require resetting other systems in the car.
- Not a Diagnostic Tool: Battery disconnection is a crude method and doesn’t provide any diagnostic information about the root cause of the problem.
Therefore, using a scan tool to erase DTCs is the recommended and professional approach for troubleshooting Mitsubishi Lancer key fob issues.
Conclusion: Getting Your Mitsubishi Lancer Key Fob Working Again
Troubleshooting a non-working Mitsubishi Lancer key fob involves a systematic approach. Starting with simple synchronization, and progressing to key fob replacement and potentially KOS-ECU replacement, you can methodically diagnose and resolve the issue.
Remember to use a scan tool for accurate DTC reading and clearing. If you are uncomfortable performing these steps yourself, or if the problem persists, it’s always best to consult a qualified automotive technician specializing in Mitsubishi vehicles for professional diagnosis and repair. A functional key fob is essential for convenience and security, so addressing these issues promptly is important for every Mitsubishi Lancer owner.
