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Ford Coil Current RFI Test

If you’re having a hard time diagnosing a misfiring Ford, the task will be made a lot easier with the aid of a Snap-on lab scope and scan tool.

The software in the scope contains a specific test just for Ford vehicles and testing their coils – it’s called the Coil Current RFI Test.

This article shows you how to get your scope and vehicle set up in order to run the test and get your results.


The test you need is in the Guided Component Tests section. Go to that, then Fuel Injection System, choose Ignition Tests, followed by Secondary Tests, and then select the Coil Current RFI Test option.

You will be advised to set the amp probe up at the 20 am setting then hook it around the coil on the battery’s positive side.

From there, pull the coil out, check it over to make sure that it’s not sparking on anything, then on your scan tool hit View Meter.

Start the car to generate a pattern on the meter, and if you need to you can also zoom out on the screen for a wider view.

Once the pattern is shown, you can scroll up in the background and take a look at an example of a good pattern before comparing it against what you are getting from your vehicle.

If you then go down a little further you will get an example of a bad pattern, which will show you instances of RFI spikes and bad noise.

If there are no spikes or noise artefacts in your pattern then this would indicate a good coil in the vehicle you’re working on.

This is a quick and easy test for you to carry out and it will really help you with your diagnostics.