EGR Valve
Secondary Air Pump
Thermostat Housing
Oil Cooler
Fuel Pressure Regulator
Blower Resistor
Heater Valve
Ignition Coil
Air Flow Sensor
Headlight Leveling Sensor
Lambda Sensor
Temperature Sensor
ABS sensor
Brake Light Switch
Oil Pressure Switch
Throttle Body
Auxiliary Water Pump

Ignition Coil

What they do
When the current is shut off (by the ignition module or the opening of the contact points in older ignition systems), the magnetic field causes a surge of high voltage (as much as 40,000 volts) in the coil's secondary windings. The high voltage passes to the distributor, then on to the spark plugs where it jumps the plug gap and fires the plugs.

Coil problems
Include shorts or opens in the internal wiring, and cracks around the high voltage terminal.