The 2003 Ford Taurus 3.0-liter, dual-overhead-cam (DOHC) engine uses a distributor-less ignition system featuring a single coil pack to fire all six spark plugs. Troubleshooting this ignition system's coil is made difficult by its location under the upper intake plenum of the engine. While troubleshooting the ignition coil pack is fairly straightforward, gaining access to it requires removing the upper plenum. The average home mechanic can complete this diagnostic project in an afternoon with the right tools.
Disconnect the negative battery cable using a 10 mm wrench. Remove the upper intake manifold according to the instructions found in your service manual. The coil is located below the upper intake manifold on the back of the engine.
Spread the locking tabs on the coil pack's electrical connector using a screwdriver and pull the connector from the coil pack. Mark and unplug the plug wires from the coil pack. Unbolt the coil from the rear of the engine using a 7 mm socket and ratchet.
Lay the coil pack on a work bench and position the coil pack so that the electrical connector is on top. Set the digital volt/ohm meter to "Ohms." Test the primary resistance of the coil pack by touching the positive (red) lead of the meter to the first pin on the left in the connector while touching the negative lead to the second pin from the left in the connector. The resistance should be .3 to 1.0 ohms.
Repeat the test for the remaining two pins by touching them individually with the negative lead on the meter. If any resistance between the first pin in the connector and the remaining three pins in the connector is more that 1.0 ohm or less than .3 ohms, replace the coil pack.
Test the secondary resistance of the coil pack by touching the positive lead of the meter inside the two plug wire terminals on the left side of the coil pack. The resistance should be 12.8 to 13.1 kilo-ohms.
Repeat the test on the center two terminals and the right two terminals. Replace the coil pack if any set of terminals has a resistance more than 13.1 k-ohms or less that 12.8 k-ohms.
