Parts for your 2020 Subaru Legacy-Ignition coils

2020 Subaru Legacy ignition coils — what they do and when to service them

Ignition coils are absolutely fitted to the 2020 Subaru Legacy. Technical sources including the Subaru Factory Service Manual (2020 Legacy/Outback — Ignition System section) and the Subaru Genuine Parts Catalogue specify coil-on-plug ignition coils for both engines offered that year — the 2.5‑litre FB25 and the 2.4‑litre turbo FA24. Each cylinder has its own coil mounted directly on the spark plug, managed by the ECU for precise spark timing.

On this model, the coils transform the 12‑volt battery supply into the high voltage needed to jump the spark plug gap under compression. That reliable spark is what keeps the flat‑four idling smoothly, pulling cleanly, and sipping fuel the way it should. Because they’re coil-on-plug, there are no traditional high‑tension leads to maintain — fewer bits to age, more consistent spark.

Ignition coils aren’t a routine replacement item on the Legacy, but they do live a hard life next to a hot cylinder head. A workshop will usually check them whenever spark plugs are due and any time a misfire code pops up. If the car shows a rough idle, hesitation on take‑off, poor fuel economy, or the check engine light with a P030x cylinder‑specific misfire, a suspect coil is high on the list.

• Diagnosis: scan for codes, inspect the coil boot for tracking or oil, swap coils between cylinders to see if the fault follows, and scope testing if available.
• Replacement: coils can be replaced individually if only one has failed, on high‑kilometre cars, replacing the full set can restore consistency.
• Best practice: fit quality OEM‑equivalent coils, change spark plugs on schedule, and keep moisture/oil out of the plug tubes.

When refitting, a light smear of dielectric grease inside the boot helps future removal and seals out moisture. Don’t over‑tighten the hold‑down bolts — they’re small, around 8 N·m is typical for Subaru coil brackets. After installation, clear any stored codes and road‑test to confirm a clean idle and smooth acceleration.

For the 2020 Legacy, keeping coils healthy is mostly about good plugs, tidy harness connectors, and promptly sorting any misfire. Treated that way, the coil-on-plug setup is robust and low‑drama for everyday Kiwi and Aussie driving.

Popular questions

Does the 2020 Subaru Legacy have individual coils for each cylinder?
Yes. Both the 2.5‑litre FB25 and 2.4‑litre FA24 engines use a coil-on-plug arrangement with one ignition coil per cylinder. This design improves spark accuracy and reduces the number of wear items compared with older coil‑pack and lead setups.

How long do ignition coils last on a 2020 Legacy?
There’s no fixed interval, many last well past typical spark plug change mileage. They’re replaced on condition — usually when a misfire code, rough running, or hard starting points to a failing coil. Regular plug changes and keeping oil out of the plug tubes extend coil life.

Should all coils be replaced at once or just the faulty one?
If a single coil has clearly failed, replacing that one is fine. If the vehicle has high kilometres or multiple intermittent misfires, replacing the full set can restore smoothness and avoid repeat visits. A trusted workshop can advise based on test results and vehicle history.