Here's a more likely breakdown of what could be wrong, in order of likelihood:
1. Fuel Delivery: Even with spark, you need fuel. Check:
* Fuel Pump: Can you hear the fuel pump prime when you turn the key to the "on" position (before cranking)? If not, the pump may be dead or the fuel pump relay is bad.
* Fuel Filter: A clogged fuel filter can restrict fuel flow.
* Fuel Injectors: While less likely to be the sole cause of a no-start (they usually give some sputtering or misfires), a completely blocked injector could prevent starting. (This is harder to check without a fuel pressure gauge).
2. Crankshaft Position Sensor (CKP Sensor): You said you changed the crankshaft position sensor, but:
* Incorrect Installation: Double-check the sensor's installation. Even a slightly misaligned sensor can cause problems.
* Faulty Replacement Sensor: It's possible the replacement sensor itself is defective. A less likely scenario, but possible.
* Wiring: Inspect the wiring harness to the CKP sensor for damage, corrosion, or loose connections.
3. Cam Position Sensor (CMP Sensor): The CMP sensor is equally crucial. A faulty CMP sensor can prevent the engine from starting, even with spark and fuel.
4. Starter Motor: Is the starter motor engaging at all? You should hear a *cranking* sound when you turn the key. If you hear a click, the starter solenoid may be bad. If you hear nothing, the starter motor itself may be faulty, or there could be a problem with the starter circuit (wiring, battery cables, etc). A weak battery can also mimic a starter problem.
5. Ignition Switch: While less common, a failing ignition switch can prevent the starter from engaging.
6. ECM (Engine Control Module): Only after eliminating all the above should you strongly suspect the ECM. While a faulty ECM *can* prevent starting, it's less likely than the issues listed above, particularly since you're getting spark. A bad ECM might exhibit other symptoms (rough running, erratic idle, etc.) before a complete no-start.
Troubleshooting Steps:
1. Check the basics: Battery voltage, battery terminals, and all fuses related to the ignition and fuel system.
2. Listen carefully: Pay close attention to sounds during the key turn. No fuel pump hum? No cranking sound? A single click? These clues are vital.
3. Visual inspection: Inspect all wiring related to the ignition, fuel system, and starter. Look for obvious damage, corrosion, or loose connections.
4. Use a multimeter: Test the fuel pump relay, check the voltage at the fuel pump, and test the CKP and CMP sensor circuits. A multimeter is essential for accurate diagnosis.
5. Consider a professional: If you're not comfortable working with automotive electronics, take it to a mechanic. Misdiagnosing and replacing parts unnecessarily can become expensive.
Replacing the ECM should be your *last resort*. Address the more probable causes first.
