Things to check *before* assuming it's the computer:
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position, crucial for timing the spark. A faulty CKP will prevent spark. This is a relatively common and inexpensive part to replace.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft. A faulty CMP will also prevent spark.
* Ignition Coil(s): These send the high voltage to the spark plugs. A faulty coil (or coils, depending on your engine) will prevent spark. Testing each coil individually is recommended.
* Ignition Coil Wiring/Connectors: Look for any damage, corrosion, or loose connections in the wiring leading to and from the ignition coils.
* Spark Plugs and Wires (if applicable): While less likely to cause a complete lack of spark to *all* plugs, worn or damaged plugs or wires can be a contributing factor. Inspect for damage.
* Ignition Switch: A faulty ignition switch may not be sending power to the necessary components.
* Fuses and Relays: Check the fuses and relays related to the ignition system. A blown fuse or faulty relay could interrupt the power supply.
Why it *might* be the computer (PCM/ECM):
* Internal Failure: The PCM itself could have failed, although this is less common than the other issues listed above.
* Software Glitch (Less Likely): While possible, a software glitch is less frequent and usually manifests in other symptoms before a complete lack of spark.
Troubleshooting Steps:
1. Start with the easiest and cheapest: Check fuses and relays first. Visually inspect the wiring and connectors for any damage.
2. Use a multimeter: Test the CKP and CMP sensors for proper voltage and signal. You can also test the ignition coils for continuity and resistance. These tests require a basic understanding of automotive electrical systems.
3. Professional Diagnosis: If you're not comfortable performing these tests, take your Jeep to a qualified mechanic. They have specialized tools to diagnose the problem efficiently and accurately. A scan tool can often read codes from the PCM that might pinpoint the issue.
In short: Don't jump to the conclusion that it's the computer. There are many simpler and less expensive components that could be the culprit. Systematically check the components listed above before considering a more costly PCM replacement.
