Owner's Problem Description
The owner recently purchased a 1999 Mitsubishi Galant that was in poor condition and wouldn't start due to a dead battery. Upon replacing the battery, the anti-theft system activated, locking the vehicle. The owner is unable to contact the previous owner and seeks guidance on unlocking the system, questioning whether a dealer visit is necessary.
Professional Technical Analysis
The 1999 Mitsubishi Galant is equipped with an anti-theft system that can activate under specific conditions, typically when a battery is replaced or disconnected. In this case, the vehicle was non-operational due to a dead battery, which was subsequently replaced. When the new battery was connected, the anti-theft system engaged, likely due to a miscommunication between the vehicle’s security system and the new battery's power source. The anti-theft system in these vehicles can often be disarmed by using the key to unlock the driver's or passenger's door, or by inserting the key into the ignition and turning it to the ACC or ON position while unlocking a door. However, if these methods fail, it indicates a deeper issue potentially involving the Electronic Timer Alarm Control ECU, located behind the fuse/relay block, which may have failed or needs to be reset. Based on the vehicle's age and its current condition, it is also important to assess the integrity of the wiring and connections around the fuse box and anti-theft control module. With regards to safety, the vehicle should not be operated until the anti-theft system is disarmed to avoid further complications.
Possible Causes
Most common causes (ordered by frequency):
- Anti-theft system activation due to battery replacement: The replacement of the battery can trigger the anti-theft system if the vehicle's security module does not recognize the power source change, leading to a locked condition. This is common in many vehicles where the anti-theft system requires a reset after power loss. - Owner reports vehicle locked after battery replacement, typical symptoms of anti-theft lockout.
- Key fob malfunction: If the key fob is not functioning or the battery is dead, it may not disarm the anti-theft system as intended. This could lead to a situation where the vehicle remains locked out despite following the standard procedures. - No response when using remote to unlock doors; potential dead fob battery.
- Electronic Timer Alarm Control ECU failure: The ECU responsible for managing the security system may have failed due to age or electrical issues, preventing the anti-theft system from disarming correctly. - Possible diagnostic codes related to alarm system failure; ECU may require inspection or replacement.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Attempt to Disarm using Key: First, try to unlock the driver’s or passenger’s door using the physical key. Insert the key into the lock and turn it in both directions (lock and unlock). This can sometimes reset the anti-theft system.
- STEP 2 - Insert Key in Ignition: If the door unlocking does not work, insert the key into the ignition and turn it to the ACC or ON position. This may disarm the anti-theft system if done correctly.
- STEP 3 - Check Key Fob: Inspect the key fob for functionality. If possible, replace the key fob battery and try using it to disarm the system again. A malfunctioning key fob can prevent the anti-theft system from resetting.
- STEP 4 - Inspect Electronic Timer Alarm Control ECU: If all else fails, locate the Electronic Timer Alarm Control ECU behind the fuse/relay block and visually inspect for any signs of damage or loose connections. A malfunctioning ECU may require replacement.
