Turn off the engine and let it cool
Disconnect the negative battery terminal
Locate the coil pack
Inspect the coil pack for cracks, burns, or corrosion
Check the electrical connector for damage or loose pins
Remove the coil pack if needed
Use a multimeter to test primary resistance
Use a multimeter to test secondary resistance
Compare readings to the vehicle service manual
Check for spark using a spark tester
Swap the coil pack with a known good one if possible
Reinstall the coil pack securely
Reconnect the battery
Start the engine and check for misfires or rough running