Here'a a how-to on testing the coil pack:
See Figures 2, 3 and 4
Fig. 2: The ignition coil connection terminal descriptions
Fig. 3: Check the primary resistance at the electrical connection and the secondary resistance across the coil towers
Fig. 4: Ignition coil terminal identification
Coil one fires cylinders 1 and 4, coil two fires cylinders 2 and 5, coil three fires cylinders 3 and 6 for the 3.3L and 3.5L engines. Each coil tower is labeled with the number of the corresponding cylinder.
Unplug the ignition cables from the coil terminals and the spark plugs. Make certain to label them before removal. Measure the resistance of the cables. Resistance must be between 3,000-12,000 ohms per ft. (30.5 cm) of cable. Replace any cable not within tolerance.
Unplug the electrical wiring harness connector from the coil pack.
Measure the primary resistance of each coil. At the coil, connect an ohmmeter between the B+ pin and the pin corresponding to the cylinders in question. Resistance on the primary side of each coil should be 0.45-0.65 ohms at 21-27°C (70-80°F). A coil not allowed to cool down, could result in inaccurate measurement results. Replace the coil with a new one if the resistance is not within tolerance.
Remove the ignition cables from the secondary towers of the coil. Measure the secondary resistance of the coil between the towers of each individual coil. Resistance for these engines depends on which manufacturer made the coil being tested. If the coil was manufactured by Diamond, the resistance should be 7000-15,800 ohms; if the coil was made by Toyodenso, the resistance should be 7000-15,800 ohms. If the coils' resistance are not within specifications, the coil must be replaced.