Secondary Ignition Circuit
WARNING: This page is about a different car, the 2009 Dodge Avenger and 2009 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.
The PCM cannot detect an inoperative ignition coil, fouled or worn spark plugs, ignition cross firing, or open spark plug cables. The misfire will however, increase the oxygen content in the exhaust, deceiving the PCM in to thinking the fuel system is too lean. Also see misfire detection. There are DTCs that can detect misfire and Ionization shorts in the secondary ignition circuit, refer to the Powertrain Diagnostic for more information.