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Fault code P0357 indicates a #7 cylinder coil circuit failure.
Possible causes are faulty ignition coil, faulty PCM, faulty wire from coil to the PCM, faulty connection at either the PCM or the coil.
A lab scope will be required to diagnose this problem. First, scope the secondary ignition system (coil output) and compare to other cylinders.
If there is no secondary output, verify proper power to the coil. If power is good, scope the Primary signal to the coil (coil trigger).
If no trigger is present, check the wire from the PCM to the coil.
If the wire from the PCM to the coil is good, replace the PCM as the driver has failed.
All of these are common problem. However, most common is a faulty coil.
The Coil On Plug (COP) works in the same manner as a standard coil pack. The COP Integrated Ignition (EI) system fires only one spark plug instead of two like standard coil packs. Since there is one coil on each spark plug, the coils will fire the spark plugs on the compression stroke only. Coils no longer fire spark plugs on the exhaust stroke.
Read more: ''97 E350, 5.4ltr. code read is p0357 ignition - JustAnswer http://www.justanswer.com/questions/...#ixzz11ju4qgMK