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Larry, Automotive technical expert
Category: Car
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Experience:  30 years automotive technical writer, editor & author
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my code is po356 ignition coil f ...

Resolved Question:

my code is po356 ignition coil f primary/secondary circuit malfunction. what do i repair. my vehicle is a 03 ford crown victoria.
Submitted: 8 years ago.
Category: Car
Expert:  Larry replied 8 years ago.
This code means there is a fault in the ignition coil on cylidner number 6.

You can test the coil circuit by removing the connector on coil nubmer 6 and probing the two terminals with a voltmeter. One terminal should show battery voltage when the key is on, the other will read open (it goes to ground when the module fires the coil).

If the coil is getting voltage, but it not firing, the coil is probably bad and needs to be replaced.

You can measure the primary resistance in the coil by using an ohmmeter to check the resistance between the two termainal on the coil (not the wiring harness). It should be less than 5 ohms. Secondary resistance can be checked between either terminal and the high voltage output terminal on the coil (where it fits over the spark plug). This should be greater than 10,000 ohms. If the coil tests out of specs, replace it.

The coil is located over teh spark plug in the cylinder head, and is held in place with a bolt.

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