1. Fuel System:
* Fuel Pump: The pump might be failing, delivering insufficient fuel pressure, or not working at all. Listen carefully near the fuel tank (you might need someone to crank the engine while you listen) for the whirring sound of the fuel pump priming. A lack of sound often indicates a faulty pump. A fuel pressure test is the definitive way to diagnose this.
* Fuel Filter: A clogged fuel filter restricts fuel flow. A relatively inexpensive part that should be checked.
* Fuel Injectors: These might be clogged, faulty, or not receiving the signal to open. Diagnosis often requires specialized tools and/or a scan tool.
* Low Fuel: Seems obvious, but always check the fuel gauge and, if low, try adding some fuel.
2. Ignition System:
* Spark Plugs: Worn, fouled, or damaged spark plugs prevent combustion. Check their condition (gap, wear, fouling).
* Ignition Coils: These deliver high voltage to the spark plugs. A faulty coil will prevent sparking in one or more cylinders. They can be tested with a multimeter or a specialized ignition coil tester.
* Ignition Control Module (ICM): This module controls the ignition system. A malfunctioning ICM can prevent the engine from starting. Requires testing with a scan tool or multimeter.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A bad CKP sensor prevents the engine from starting. Requires testing with a scan tool or multimeter.
* Cam Position Sensor (CMP): Similar to the CKP sensor, but monitors the camshaft's position. A faulty CMP sensor will usually cause a no-start condition. Requires testing with a scan tool or multimeter.
3. Computer/Electrical Issues:
* PCM (Powertrain Control Module): The computer that controls the engine. A faulty PCM can cause a wide range of problems, including a no-start condition. Diagnosis typically requires a scan tool to read fault codes.
* Battery/Alternator: While cranking indicates some battery power, a weak battery or failing alternator might not provide enough juice to start the engine reliably. Check battery voltage and alternator output.
* Fuses and Relays: Check fuses and relays related to the fuel pump, ignition system, and PCM.
4. Security System:
* Immobilizer: If the vehicle has an immobilizer system (common in 2003 models), a problem with the key fob or system could prevent starting.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any fault codes stored in the PCM. This is the most important first step.
2. Check the basics: Fuel level, battery voltage, and obvious visual checks (loose wires, damaged components).
3. Listen for the fuel pump: Does it prime when the key is turned to the "on" position?
4. Check spark: (With caution!) Inspect spark plugs for spark. Requires removing spark plugs, grounding them to the engine block, and having someone crank the engine while you observe sparks (if any).
Recommendation:
If you're not comfortable working on cars, take it to a qualified mechanic. They have the tools and experience to diagnose the problem efficiently and accurately. The cost of misdiagnosing the problem yourself could easily outweigh the cost of professional diagnosis. Providing the DTCs from a scan tool will greatly assist a mechanic.
