Yes, a failed coil pack is a very common reason a car won't start. The coil pack's job is to transform the battery's low voltage into the thousands of volts needed to create a spark at the spark plugs. If it fails completely, no spark is generated. Without a spark, the fuel in the cylinders won't ignite, and the engine simply cannot start. You'll often hear the starter motor cranking the engine normally, but it will never "catch" and run on its own.
A bad coil pack often shows warning signs before it fails completely. You might experience an engine misfire, which feels like shaking or stumbling during acceleration, especially under load. This can trigger the check engine light to flash. Other symptoms include a rough idle, a noticeable loss of power, and worse fuel economy. If you ignore these signs, the problem can escalate from a single-cylinder misfire to a complete no-start situation if the coil pack fails entirely or if its failure affects multiple cylinders.
Diagnosing this issue requires some basic troubleshooting. A simple way to check is to listen to the engine cranking. If it cranks quickly and healthily but doesn't start, and you don't smell a strong odor of gasoline (which would point to a flooding engine or faulty fuel pump), a spark issue is likely. While a professional mechanic would use an ohmmeter to test the coil's resistance or a spark tester to check for spark, these methods can be dangerous for a novice. The safest first step is to use an OBD2 scanner to read any trouble codes. Codes like P0300 (random misfire) or specific cylinder misfire codes (e.g., P0301) can point directly to a coil problem.
| Symptom | What It Indicates | Common Diagnostic Trouble Codes (DTCs) |
|---|
| Engine cranks but won't start | Likely no spark being generated. | P0350 (Ignition Coil Primary/Secondary Circuit Malfunction) |
| Check engine light flashing | Active engine misfire occurring. | P0300 (Random/Multiple Cylinder Misfire) |
| Rough idle and shaking | One or more cylinders not firing correctly. | P0301-P0312 (Cylinder-specific misfire codes) |
| Loss of power and poor fuel economy | Incomplete combustion due to weak/no spark. | Often accompanied by misfire codes. |
Replacement is usually the solution. Coil packs are typically not repaired. It's also a good practice to replace the spark plugs at the same time, as worn plugs can put extra strain on the new coil pack.
