Parts for your 2015 Subaru Forester-Ignition coils

2015 Subaru Forester — Ignition Coils

Ignition coils are indeed fitted to 2015 Subaru Forester petrol models. According to the Subaru Forester (SJ, MY2015) Service Manual — Engine (Ignition System), the FB20/FB25 and FA20F/DIT petrol engines use individual coil‑on‑plug ignition coils (one per cylinder). Subaru’s MY2015 parts catalogue also lists four ignition coil assemblies for these engines. By contrast, the EE20 2.0D turbo‑diesel variant does not use ignition coils because it has a compression‑ignition system with glow plugs instead (Subaru Service Manual — Diesel Engine EE20).

On petrol Foresters, the ignition coils are the quiet achievers that turn battery voltage into the serious spark energy needed to fire each plug. With a coil sitting directly on each spark plug, the setup reduces energy loss and helps the engine start cleanly, idle smoothly, and pull strongly when you put your foot down. If a coil starts to fade or fails, you’ll usually notice a rough idle, a hiccup under load, a drop in fuel economy, or a check engine light with misfire codes (often P0300–P0304).

There’s no fixed replacement interval for coils on the 2015 Forester — they’re generally replaced when they show symptoms or test out of spec. As part of routine servicing, it’s smart to inspect the coil boots when changing spark plugs, check for oil in the plug tubes (from a leaking rocker cover gasket), and look for heat‑cracking or carbon tracking on the boots. Keeping moisture and debris out of the plug wells goes a long way to coil longevity.

When a coil is confirmed faulty, replace the affected unit and clear the codes, then road‑test to confirm the fix. There’s no hard rule to replace all four at once, many owners do fine swapping a single failed coil, though higher‑kilometre cars may benefit from doing pairs or a full set for peace of mind. Always seat the coil squarely on the plug, avoid levering on the plastic body, and tighten the retaining bolt to the factory torque spec in the workshop manual. A tiny smear of dielectric grease on the inside of the boot can help future removal and seal out moisture. Good plugs, healthy battery voltage, and clean grounds all help the coils do their job reliably across Aussie and Kiwi conditions.

How long do ignition coils last on a 2015 Subaru Forester?

Many coils run well past 150,000 km, but heat, oil in the plug tubes, and age can shorten their life. If the car is driven mostly in hot stop‑start traffic or tows regularly, expect a bit more wear on ignition components. Regular plug changes and keeping the plug wells clean helps them go the distance.

Do coils need to be replaced in sets?

Not necessarily. It’s common to replace just the failed coil and monitor. If the vehicle has high kilometres and multiple coils are ageing, replacing them as a set can save future downtime — it comes down to condition, budget, and how long the Forester is expected to be kept.

Can a bad coil damage the catalytic converter?

Yes, if a misfire is ignored. Unburnt fuel from a persistent misfire can overheat the converter. If there’s a misfire code and rough running, it’s worth diagnosing promptly — coils, plugs, and even a simple vacuum leak check can prevent bigger repair bills.