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Quick Tip: Ignition Coil Current and Voltage Comparison

Applies To: MODIS Edge™, MODIS Ultra™, VANTAGE® Ultra, VERUS® Edge, VERUS® PRO, ZEUS®

Having a hard time figuring out whether or not an ignition coil is bad? In this Diagnostic Quick Tip, National Field Trainer Jason Gabrenas shows you how to compare both the voltage and the current of an ignition coil to find a problem quickly.



When testing ignition coils, there's a couple of different ways we can test: we can do voltage, we can do amperage.

Wouldn't it be nice to be able to compare the voltage and the amperage flowing through the circuit at the same time?

We're going to do a two-channel test here. One channel is going to have the primary voltage and the other channel is going to have the primary current going through it. We're going to see how they compare on the screen.

I already have the coil all set up. I have channel one going to the voltage and I have channel two hooked up with a low amps current probe.

Let's just put the scan tool in record then fire up the car and see what happens. After a few seconds, pause the recording and shut the vehicle off.

Let's move this zoom up a little bit so we can compare them. You can see the current is going on the green wire and the voltage is going on the yellow wire. They should pretty much match up because voltage and current follow each other around.

As we can see, they do line up nicely and the current pattern looks good and the voltage pattern also looks good. So this coil is good.

Last Updated: January 17, 2020

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