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!

18 COMMENTS

  1. My Subaru misfire condition wont go away even after Ive completed thus How to guide. What else can it be? Please help!

    • 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?

  2. 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.

  3. 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

  4. I have a 1991 Subaru Loyale, I replaced coil, Distributor, Computer, still no spark! I have purchased two manuals on this car, yes 2. And I have yet to find the cam sensor or angle sensor or where in the world they are or even what they look like. The books don’t even show where or what they look like! Any help out there? yes I have juice to coil .

    • Hi John, sorry to hear about your Forestor ignition coil issues.

      So, let’s start at the beginning. The cam sensor is located on the left side of your engine, and mounted near the front of the engine / timing components. This reads the intake cam from your Subaru. The crank sensor is located on the front of your engine, near the crank snout / pulley. I would check these 2 components first before replacing anything else.

      Hope that helps! Thanks for reading

  5. Thanks for this!
    My issue is straight forward; Pin 1 and 2 sparks while Pin 3 and 4 doesn’t. Sometimes, Pin 3 and 4 sparks and fail again.
    I bought another ignition coil and the situation is exactly the same.
    Will changing the entire engine solve this problem? Or what can be done fix this issue?
    Please help!
    Thank you

    • Hi Charlie, thanks for reading.

      I would begin by checking the wiring in your Subaru Forester Ignition coils, specifically from your ignitor to your coils. Sounds like you have an intermittent wiring issue, or perhaps a bad ground. Start with the engine harness or the ignition subharness and go from there. Hope that helps!

  6. I’m having an issue where putting the leads for the multimeter makes no change to the readings. I know the tool works because I can see that I have 11.0 ohms in the secondary windings. But no readings at all for the primary

  7. I’m testing ohms between a and b and between c and d and I’m getting around 12 ohms. You say it should be .7 ohms. What could be the cause?

  8. Hi…. My friend has a 2000 Forester…. Took it to autozone to get a reading of problem…. Bad ignition coil…. Then went to O’Reillys to get the part… Installed it and was working so decided to take it on highway (all in one day) 40 minutes into ride we Stopped at gas station… It stopped and started fine… Back on highway and about an hour into the ride….. The car lost power…. Coasted to the side of highway and now it won’t start…. The lights work but nothing happens when trying to start engine…….. What’s up????

    • Hi there, can you check the car for spark? Take a spark plug and rest it against a valve cover. Have a friend crank and make sure you are safe and that there’s no fuel around. This should show if you are getting spark or no spark in your Subaru.

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