Ignition
Ignition Coil
The ignition coil transforms battery voltage into the tens of thousands of volts needed for the spark.
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Ignition flow
Interactive — tap a partTap a part to see how it fits in the system.
What it does
- Steps up 12 V to 20,000–45,000 V
- Delivers the spark to the plug at the right time
- Modern coil-on-plug design sits directly on each plug
When it fails
- Misfire on one cylinder
- Loss of power
- Check engine light flashing
- Engine shakes under load
How to diagnose
- Swap the coil to another cylinder: if the code follows, the coil is bad
- Measure primary and secondary resistance
- Check the connector and wiring
Maintenance
- Replace coils in pairs or as a set when more than one fails
- Keep plug boots clean and dielectric-greased
Use the diagnosis order. When a part fails, confirm each hypothesis with measurements before replacing anything — codes and symptoms overlap.