How To Test a Subaru Forester Ignition Coil

How To Test a Subaru Forester Ignition Coil

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Problems with your Forester Ignition Coil can cause serious issues with your 2.5 liter Subaru engine. Some of these Subaru Forester problems can range from intermittent engine misfire issues or your Forester not starting. This coil pack is mounted to the top of your engine, and failure of these coils are relatively common.

Today I’ll be showing you how to test the Forester ignition coil in your 2000 Subaru. To do this however you’ll need a digital multimeter to measure resistance of the coils. If you have misfire make sure that you check your crank and cam angle sensors before continuing onto your Subaru coil pack.

Test a Subaru Forester Ignition Coil 1When your Forester has an issue with the coilpack, chances are the check engine light will lit up. When you see this check engine symbol on your dashboard, you’ll need the right scan tool to pull your code.

If you determine that your OBDII trouble code is ignition coil related, this guide is for you.

While you are testing your Forester ignition coil you should also inspect your spark plugs and spark plug wires. If you see any issues with these components, replace them right away.

Symptoms of a bad Forester ignition coil

Because this ignition coil pack is mounted to the top of your boxer engine failure is fairly common. Exposed to the heat and vibration in your engine bay, this procedure can help you test the coil packs. Here’s a few of the other Subaru Forester issues that might come up from failed spark plug coils.

  • Poor performance
  • Black smoke from exhaust
  • Failed emissions test
  • Engine misfire
  • Check Engine Light ON

Testing your Forester ignition coil pack

To begin our comprehensive ignition testing guide, you’ll begin by testing the coil pack internal resistance. There’s two ways to go about this. First open your hood and locate the coil pack. Unplug your Forester ignition coil pack.

Test a Subaru Forester Ignition Coil 2

Once you’ve disconnected the four wire pin connector, you will be using your multimeter to measure resistance. You do this at the four wire connector at the face of your coil packs.

Test a Subaru Forester Ignition Coil 3Place the leads of your multimeter to PIN A and PIN B. You should have 0.73 Ω ± 10% between these two pins on the Forester ignition coil.

Now check PIN C and PIN D and the measurement should read the same. If your resistance reads below this mark, it’s a sign of an open condition or a short in your Subaru ignition coil packs.

Now that you’ve tested for internal resistance at the terminal pins, you must also check the secondary resistance at the spark plug leads. These leads correspond to the Forester ignition coil terminals you just tested.

Testing for secondary resistance in coil pack

The next step of this DIY guide is to measure resistance at the spark plug wire terminals. Much like the wiring connector above, this is done in pairs using the Forester ignition coil diagram below. Crank your multimeter down a notch and probe at the pairs shown to measure secondary resistance.

Test a Subaru Forester Ignition Coil 4

The resistance at these spark plug coil pairs should read 12.8 kΩ ± 15% for either pair. If any of the measurements of your Forester ignition coils do not match these specifications, it’s a sign your coil has gone bad. Remove the four bolts that hold this coil pack in place, and install your replacement coil pack.

Have any questions about this Forester ignition coils testing guide? Leave us a message below and let us know!

6 COMMENTS

    • Hi David! Thanks for reading!

      If you have a misfire in your Subaru, have your tried load balancing your EJ engine by unplugging your spark plugs one at a time? Have you checked the spark plugs and the wires to see if there’s a misfire problem coming from that?

  1. So I was excited when I first read this article, as I thought I had diagnosed my forester sudden no start and no spark on coil side 1 and 2.

    I am no electrical expert, but when I tested pins c and d my meter did something funny, vs the readings on pin a and b. So i purchased a new coil. But when I tested the new coil I got the same readings out of the c/d pins. I think C pin is power in? I have not installed the new coil as I might loose return option.
    I also have codes P0340, and P0341. Hope I didnt slip or loose timing belt.

  2. On my 01 forester i disconected the no.1coil wire from the coil and no fire but no.2,3,and 4 were fine so then i checked the primary and got a 9.4 reading on a&b and nothing on c&d. I then checked the secondary and all was within specs is this my coil or could something else be causing this problem

    • Hi Kenny, thanks for commenting.

      are you getting misfire in your Forester or a check engine light for misfire? What are the symptoms of your Subaru Forester ignition problems? Let us know and we can help point you in the right direction! Let us know how it turns out and thanks for reading our DIY Subaru Forester Ignition Coil guide.

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