Re: 2007 JK no spark at coil on #1 & #4 cylinders
The ECM indeed supplies the ground for the ignition coils, but it would be wise to check the voltage side first. The voltage to the coils is switched via the ASD relay ( auto shut down). When ignition is switched to run, the ASD relay will be powered, but when not started, it will fall off after some seconds. If power is available there, you could measure the ground wire from the coil to the ECM for continuity. If this also is ok, then most probably the ECM is faulty.