* PATS Key Transponder Failure: The most common cause. Your key fob contains a transponder chip that communicates with the vehicle's receiver. If the chip is malfunctioning, damaged, or the key is not properly recognized, the system will disable the starter. The blinking light is the system's way of indicating this failure.
* Receiver Issues: The receiver in your truck that communicates with the key's transponder might be faulty. Dirt, damage, or a failing component could prevent it from reading the key's signal.
* Wiring Problems: Damaged or corroded wires in the PATS system can interrupt the communication between the key and the receiver. This is less common but possible.
* Battery Issues (Low Battery): While less likely to be the *primary* cause of the blinking light, a very low battery can sometimes interfere with the PATS system. A weak battery might not provide enough power for the transponder signal to be reliably read.
* Body Control Module (BCM) Problems: The BCM controls many aspects of the truck's electrical system, including the PATS. A failing BCM can cause various issues, including the anti-theft system malfunctioning. This is less frequent but possible.
What to Do:
1. Try a Different Key: If you have a spare key, try starting the truck with it. If it starts, the problem is almost certainly with the original key's transponder.
2. Check the Battery: Make sure the battery is fully charged. A weak battery can sometimes lead to issues with the PATS system.
3. Have the System Checked: A professional mechanic, especially one familiar with older GM vehicles and PATS systems, is the best resource. They can properly diagnose the problem, whether it's a key replacement, receiver repair, wiring issues, or BCM problems. They have tools to read trouble codes that might point directly to the fault.
Don't attempt extensive DIY repairs unless you are experienced with automotive electronics and security systems. Incorrect wiring can damage the system further.
