2003 Ford Expedition 5.4 coil over plug system with a misfire and a P0356 trouble code. This is a very good case study on how to deal with shorted ignition coils. You need to be aware that a shorted primary winding in an ignition coil can damage the computer transistor driver. In this video I will show you how to identify a shorted ignition coil and also how to test the coil control circuit. The control testing is the same regardless of the location of the driver. So the same procedures can be followed for igniters, modules and computer controlled coils.

Engine Performance Diagnostics chapter 22

symptoms 50

  • misfire (constant)
  • check engine light (P0300, P0174, P0356)

fix 50

  • replace shorted ignition coil and damaged engine computer

test shown enh 50

  • wiring diagram review of the ignition system
  • how to measure coil primary current for all of the coils in a central location
  • coil primary current ramp tests with a scope
  • how to synchronize coil firings to identify the problem cylinder
  • how to check for an open coil control wire
  • how to test for a damaged computer transistor driver

Tools used

  • scan tool
  • Picoscope
  • inductive low amp probe
  • backprobing tools

end faq

Playlist

(Chapter 22) No Spark Troubleshooting, Ignition Coil & Module Testing

Related videos:

How to test for a shorted ignition coil (Honda Distributor):

How to find a shorted coil on a Ford 5.4 engine (misfire diagnosis):

How to identify a shorted ignition coil (Honda):

How to test for a shorted ignition coil with a scope (Lexus):

How to test an ignition coil/module with a test light (distributor ignition) - GM :

end faq


For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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