For coils used before 1999, you should first use numbered tape to mark the wires and terminals before removing the primary and high-tension wires from the coil. Take out the coil assembly, clear its outside shell, look for any cracks or parts that won't work. Check the primary and tower terminal of the coil for rust, then wipe away any damage. Use an ohmmeter to check the coil primary resistance and compare it with the expected numbers; also do the same for its secondary resistance. When the measurements from our sensors are off, we need to replace the component. Check every wire lead and coil connection for any dirt, corrosion, or water damage before you put the coil back. With your ignition off, disconnect the wires from the coil. Then, measure both primary and secondary resistances. Replace the coil when you find incorrect readings with a breakerless system. Take the primary winding's resistance between the coil and the case. If the resistance falls below what's recommended, buy a new coil. Start with battery disconnect, then unhook the cable from the negative terminal. Unbutton the primary wire clamps, smaller cans, and coil from its place. Reinstallation follows the reverse order. When fixing EDIS systems, pull out all electrical plugs and check that the coil terminals measure the same resistance as stated by the manufacturer. Pinpoint resistance in each coil pack by touching one terminal of each pair. To change the ignition coil, start by taking off the black negative battery terminal. Then, disconnect the wire connectors from the ignition coil. Move slowly, as you work to disconnect the wires from their joint. Reconnect the ignition coil's bolts and replace it using the same steps, but push the spark plug wires back onto the rubber boot, covered with silicone dielectric compound.