Hard to read the complete code in that photo, but I'm guessing it is P1358. It involves the secondary circuit of the ignition coil for the rear cylinder being intermittent. That could mean you have a misfire on that cylinder, or it could just mean you have an intermittent loss of continuity in the circuit. Question #1: Are you running stock plugs and wires, or aftermarket? If aftermarket, the circuit resistance could be affected enough to cause a false code (assuming the engine really isn't misfiring), so you may want to try changing back to stock parts. If stock, check the plug wire connections at both ends. Something as simple as a loose or corroded connection can trigger these codes. You can also measure the actual resistance of the plug wires and compare to factory specs. I don't have a 2003 manual, but for reference the spec for my 2005 is 4975 - 11960 ohms for a 20 inch long plug wire.
Jerry