The ignition coils in a four-cylinder engine are housed in the coil pack, with coils '1' providing voltage to cylinder one and four, and '2' to cylinders two and three. The first step as described will involve identification of the spark plug cables then removal of the coil pack cables and lastly; removal of the primary wiring electrical connector. Check the amount of primary resistance of each coil with an ohmmeter between the center terminal and each outer terminal, record the readings, and compare with the specifications; if the resistance differs, then change the coil. Next, use the ohmmeter and connect the two terminals by switching the spark plug wire to terminal 1 and repeat on terminals 2 and 3 and compare to specifications and if fails, replace the coil. Last but not the least, reconnect the spark plug wires back and reconnect the primary wiring electrical connector. To work on V6 engines, first, you need to take out the air cleaner assembly as well as the EGR tube; you also need to remove each spark plug wire from the 
Distributor cap but before you do so label them. Take out the distributor cap screwed and undo the primary wiring electrical connector. Check the coil primary resistance with the probe between the terminals of the two-pin connector; if the actual resistance is not within the specifications, replace the whole distributor as the coil is non-repairable. Check coil secondary resistance between coil hi-tension tower terminal and both terminals of two pin connector and replace the distributor if it falls in the above said range. Replace the distributor cap and its parts in a backward manner as listed above. In four-cylinder engines for removal, label and remove spark plug wires, disconnect the primary wiring electrical connector, remove the coil pack mounting nuts and lift the coil pack off the valve cover, while for reinstallation the procedures is the reverse of the above. For V6 engines, if the ignition coil is bad, it's impossible to replace a single component; the distributor will have to be substituted.