Parts for your 2012 Subaru Forester-Ignition leads

2012 Subaru Forester ignition leads — are they used, and what to service instead

For the 2012 Subaru Forester (SH series in Australia and New Zealand), traditional ignition leads are not used. Technical documentation confirms this: the Subaru Service Manual for SH Forester (MY2011–2012) shows both the naturally aspirated FB25 engine and the turbocharged EJ255 using a coil-on-plug (COP) setup, with an individual ignition coil mounted directly on each spark plug. Subaru wiring diagrams from Subaru Technical Information System (STIS) depict four separate coil drivers rather than a single remote coil and high-tension leads, and the Subaru parts catalogue lists individual ignition coil assemblies and spark plugs but no ignition wire set for this model year.

Why no leads? With coil-on-plug, the high-voltage path is extremely short: the coil sits on the spark plug, so there’s no need for long, resistive high-tension leads. This improves spark energy at the plug, reduces electromagnetic interference, and cuts down on misfire risk caused by aged or cracked leads. It also frees up space around the flat-four engine and reduces maintenance items for owners.

What should owners of a 2012 Forester look after instead? Focus shifts to the spark plugs, the coil packs, and the rubber boots that seal the plug wells. Routine servicing should include:

• Replacing spark plugs at the interval specified in the owner’s manual (iridium plugs typically have a longer service life, NA and turbo intervals differ).
• Inspecting COP boots for hardening, cracking, carbon tracking, or oil contamination from rocker cover gasket weeps.
• Checking coil connectors for secure fit and no green corrosion, ensure loom clips are intact.
• Scanning for misfire codes (P0301–P0304) and addressing any rough idle or hesitation under load.

When replacing plugs, use the correct heat range and spec (as per Subaru), apply a small dab of dielectric grease inside the boots, and torque the plugs and coil hold-down bolts to spec to avoid thread or coil damage. If a misfire points to a single cylinder, a quick coil “swap test” (moving the suspect coil to another cylinder) can help confirm a failing coil. Genuine or reputable OE-equivalent coils are recommended to maintain reliable hot and cold starts.

These points are supported by Subaru’s SH Forester Service Manual (Engine/FB and Engine/EJ Ignition sections), STIS wiring diagrams for MY12, and regional Subaru parts catalogues listing individual ignition coils and no high-tension lead sets for the 2012 model.

Popular questions

Does a 2012 Subaru Forester have ignition leads?
No. Both the FB25 (2.5 non-turbo) and EJ255 (2.5 turbo) engines use coil-on-plug ignition, so there are no separate high-tension leads to replace. Service attention goes to the spark plugs and the individual coil packs.

What should be replaced during an ignition service on a 2012 Forester?
Typically, spark plugs at the manual’s interval, plus inspection of the coil packs and boots. Any coil showing cracking, oil-soaked boots, or causing a cylinder-specific misfire should be replaced. Always use plugs and coils that meet Subaru specifications.

What are common signs of a failing ignition coil on this model?
Rough idle, hesitation under load, increased fuel use, and a flashing or steady check engine light with codes like P0301–P0304. A swap test and scan data (misfire counters) can help pinpoint the faulty coil.