Turn off the engine and disconnect the battery negative terminal
Locate the ignition coil
Inspect the coil for cracks, burns, swelling, or corrosion
Check the coil connector and wiring for damage or looseness
Remove the coil if needed for testing
Use a multimeter to measure primary resistance across the coil terminals
Use a multimeter to measure secondary resistance between the high-voltage terminal and a primary terminal
Compare resistance readings with the manufacturer specifications
Check for spark using a spark tester
Verify power and ground at the coil connector with a multimeter
Swap the coil with a known good coil if available
Reinstall the coil securely after testing
Reconnect the battery and clear any fault codes if necessary