Possible Causes:
* Passlock System Issue: The 2004 Impala likely uses a Passlock system. This system uses a resistor in the ignition key to authenticate the key. If the new switch isn't compatible with the existing Passlock system, or the resistor isn't correctly aligned, the system will reject the key and the security light will flash.
* Incorrect Installation: The ignition switch might be incorrectly installed. Even a slight misalignment can prevent proper communication.
* Damaged Wiring: During installation, you might have accidentally damaged wires related to the ignition system or the Passlock system.
* Faulty Ignition Switch (Despite being New): While less likely, it's possible you received a defective new ignition switch.
* PCM Issues: In rare cases, the problem might lie with the PCM itself. This is less probable, but possible.
Troubleshooting Steps:
1. Double-Check Installation: Carefully re-examine the ignition switch installation. Consult a repair manual or online diagram for your specific Impala model to ensure everything is properly connected and seated. Pay close attention to any wiring harnesses.
2. Check for Damaged Wiring: Inspect all wiring connected to the ignition switch and related components for any damage (breaks, shorts, loose connections). Repair or replace any damaged wires.
3. Key Programming (If Applicable): Some ignition switches may require programming to the vehicle's system. This usually requires specialized equipment. If your new switch requires programming, you'll likely need to visit a locksmith or dealership.
4. Try a Different Key: Test the car with all available keys. If one key works and others don't, it's a strong indicator of a Passlock problem related to the key, not necessarily the switch.
5. Check the Passlock Sensor Ring: This is a small ring around the ignition cylinder that contains the resistor. Ensure this is properly seated and functioning. Damage or misalignment can also cause issues.
6. Professional Diagnosis: If you've tried the above steps and the security light continues to flash, it's best to take your car to a qualified mechanic or dealership. They have diagnostic tools to identify the precise cause of the problem. They can properly check for problems with the Passlock system and/or PCM.
Important Note: Working on the vehicle's electrical system can be dangerous. If you're not comfortable working with car electronics, it's best to leave the repair to a professional. Attempting repairs without the proper knowledge and tools could cause further damage.
