Here's why and what you can try:
* Passlock Failure: The Passlock system uses a resistor in the ignition key to communicate with the car's computer. If this resistor is faulty (in the key or the receiver), the system won't recognize the key, and the engine will shut off immediately. This is very common in older Pontiacs.
* Other possibilities (less likely given the security light): While less probable with the security light illuminated, consider these:
* Crankshaft Position Sensor (CKP): A faulty CKP sensor won't allow the engine to start.
* Cam Position Sensor (CMP): Similar to the CKP sensor, a faulty CMP can prevent starting.
* Fuel Pump Relay or Fuel Pump: Though you say you have gas, a faulty fuel pump or its relay could still be the problem. A quick check of the fuel pump fuse is in order.
* Ignition Switch: A failing ignition switch can interrupt the electrical signal to start the engine.
What to do:
1. Try all your keys: Sometimes, it's a simple matter of using a different key if you have more than one.
2. Check the Passlock System (Most Likely Solution): This requires some automotive knowledge. You might need to:
* Replace the ignition key: This is the most common and often easiest solution. You'll need a new key programmed for your car. A locksmith or dealership can usually handle this.
* Replace the Passlock module: This is a more involved repair and may require a professional.
3. Check fuel pressure: If you're comfortable working on cars, you can check fuel pressure to rule out fuel pump problems.
4. Have it professionally diagnosed: If you are not comfortable doing this yourself, take your car to a mechanic. They will have the diagnostic tools to pinpoint the exact cause and make the necessary repairs.
Since the security light is on, focusing on the Passlock system is the best starting point. If the key is definitely the problem, replacing the key is much cheaper than replacing other components.
