Several tests can be done to test an electronic ignition coil, including a standard coil test, primary circuit switching test and ignition coil resistance. These tests will test the resistance felt on the ignition coil when it is connected to an outside power source.
To perform a standard ignition coil primary resistance test, the ignition should be off in the car. Once the two low voltage coil terminals are disconnected, the resistance should remain between 0.3 and 1 ohms.
A switching test uses a 12 VDC test lamp. A small straight pin should be inserted into the wire that runs the negative coil to the TFI module. The pin can then be connected to the lamp. If the lamp flashes, more circuit tests need to be performed. If the light simply lights up, a wiring harness test should be performed. If the light does not come on at all, the continuity of the primary circuit should be tested.
Ignition coil resistance tests are used on the secondary aspects of the ignition coil. These tests should be performed with caution because the circuits of the secondary part of the ignition can have very high voltage. These tests should only be performed if there was inconclusive evidence in any of the primary tests.