A coil might seem to be misfiring or not firing at all, or the Powertrain Control Module (PCM) is Reading a Diagnostic Trouble Code (DTC) of a misfire so changing the coil with one adjacent could help. When the suspect coil caused a DTC on one of the cylinders, it will probably introduce the same DTC when mounted over another cylinder, indicating the coil itself is most likely defective because it is unlikely that the harnesses on two ignition coils on the same cylinder would both fail. On V6 engines, when replacing, disconnect cable on one of the negative battery terminals, remove engine cover/air filter housing (where needed), disconnect electrical connector on ignition coil and on certain models, label the spark plug wires then disconnect them. Unscrew the ignition coil mounting bolt and coil take those off, and look at the rubber boot to see if it is damaged. Then do the same procedure, but on 2006 and later models it is also necessary to look at the state of a rubber boot. The opposite as removal is installation and once this has been done, carry out relearn processes. In four-cylinder engines, it is started in the same way; the negative battery terminal is disconnected, individually screwing that electrical connector off plus ignition cover screws or engine cover screws on some engines, with the ignition coil mounting bolts removed. Check the rubber boot and, when required, re-fit, then, in reverse order, re-check all re-fit parts.