1. PATS System (Most Likely Culprit):
* Key Fob Battery: The simplest thing to check first is the battery in your key fob. A weak battery can cause intermittent problems with the PATS system. Try replacing the battery and see if that resolves the issue.
* Key Recognition: The car's computer might not be recognizing your key. Try all your keys, if you have multiple. If you only have one key, consider having a Ford dealership or locksmith program a new key. A damaged transponder chip inside the key is also a possibility.
* PATS Module Issues: The PATS module itself could be malfunctioning. This is a more complex issue and usually requires professional diagnosis. A scan tool capable of reading Ford's proprietary codes is needed.
* Wiring Issues: A problem in the wiring between the ignition switch, the PATS module, and the engine control module (ECM) can prevent the car from starting. This could be a short, corrosion, or a broken wire. This requires careful inspection by someone familiar with the Mustang's wiring harness.
2. Other Electrical Issues:
* Security System (Aftermarket): If you have an aftermarket security system installed, it might be interfering with the starting process. Check the system's documentation or try temporarily disconnecting it (carefully) to see if it's the cause.
* Immobilizer: Even if not the PATS system, the car might have another type of immobilizer that's preventing it from starting.
* Battery: While you've said the car turns over, a weak battery might not provide enough power to the starter even if it cranks the engine. Have the battery load tested at an auto parts store.
* Starter: Though the car is cranking, the starter itself could be failing. A failing starter might not engage fully, preventing the engine from turning.
* Fuel Pump: A malfunctioning fuel pump, fuel pump relay, or a fuel delivery issue (clogged filter) can prevent the engine from starting even if it cranks.
Troubleshooting Steps:
1. Key Fob Battery: Replace the battery in your key fob.
2. Try all keys: Test all available keys to see if one is recognized.
3. Visual Inspection: Check for any obvious wiring issues under the dash and around the ignition switch. Look for any signs of damage, corrosion, or loose connections.
4. Professional Diagnosis: If the problem persists, take your Mustang to a qualified mechanic or Ford dealership. They have the proper diagnostic tools to determine the exact cause of the problem, especially if it's related to the PATS system. Explain the buzzing sound and the no-start condition clearly.
Important Note: Avoid continuously trying to crank the engine. This can drain your battery and potentially cause further damage. If the car isn't starting, give it a rest before trying again.
