* Aftermarket Alarm System: If your Blazer has an aftermarket alarm system (not factory-installed), you'll need to consult its owner's manual. The reset procedure varies wildly depending on the brand and model. Look for a small switch, keypad, or possibly a sequence of button presses on the key fob.
* Factory Security System (Passlock System): This is more likely the culprit. The 1999 Blazer uses a Passlock system, which is integrated into the ignition system. It doesn't have a separate alarm that sounds. Instead, it prevents the engine from starting if it detects unauthorized key use. Problems usually stem from:
* Weak Battery: A weak battery in the vehicle or the key fob can trigger the Passlock system. Try jump-starting the Blazer with a good battery. Replace the battery if it's old or weak. A new key fob battery could also solve the problem.
* Key Problems: A worn or damaged key can also cause issues. Try using a spare key if you have one. If the problem persists, you may need to have the key reprogrammed or replaced at a dealership or locksmith specializing in automotive keys.
* Passlock Sensor Issues: The Passlock sensor itself can fail. This is less common but requires professional diagnosis and repair. A mechanic with diagnostic equipment will be needed to test the system.
* Security System Failure: In rare cases, the Passlock system itself might have a fault. Again, a mechanic will be needed to diagnose and repair this.
What to Do:
1. Try your spare key: This is the easiest first step. Does it start the truck? If so, your primary key is likely the problem.
2. Check the battery: Make sure the Blazer's battery is adequately charged. Jump-starting it might solve a low-voltage issue.
3. Consult your owner's manual: While it might not explicitly detail a "reset," it might offer troubleshooting steps for starting problems related to the security system.
4. Visit a locksmith or dealership: If none of the above works, professional help is needed. They have the tools and knowledge to diagnose and fix Passlock issues.
Important Note: Avoid attempting to bypass or disable the Passlock system yourself. Doing so improperly could damage the vehicle's electrical system or even make the security system more problematic.
