Restore clean high-voltage insulation between coil and plug with the ThunderCore PRO Coil Boot 900-P2101, an OE-replacement boot for coil-on-plug (COP) and coil-near-plug (CNP) ignition systems. It drops in as a direct-fit replacement for the 2006 Saab 9-2X, 2004-2006 Subaru Baja, 2004-2010 Subaru Forester, 2004-2014 Subaru Impreza, 2005-2009 Subaru Legacy, and 2005-2009 Subaru Outback — see the "Vehicles it fits" section for engine-level fitment.
In COP/CNP setups, the coil boot forms the insulative path between the ignition coil and the spark plug. Over time boots can degrade from heat, vibration, or chemical exposure, which can lead to arc-through, misfires, or hard starting. If a worn boot is the cause of those symptoms, this replaces it and helps keep spark energy isolated on its way to the plug.
- Heat & Chemical Resistant: built from high-temp silicone and reinforced materials to resist oil, fuel, and under-hood heat.
- Restores Ignition Insulation: replaces worn or cracked boots to help maintain proper spark isolation and reduce voltage loss.
- OE Replacement Quality: engineered to match OE dielectric strength, boot length, and connector geometry.
- Exact OE Fit: designed to work with factory ignition coils and spark plugs in coil-on-plug and coil-near-plug systems.
When servicing an ignition tune-up, consider replacing the boots across all cylinders for consistent insulation.
Interchange: 671-4306 · 36-2084 · 36-2112
SPP121E · 6714306 · 362084 · 362112
This part cross-references / interchanges with the following part numbers:
671-4306, 36-2084, 36-2112, SPP121E
Frequently Asked Questions
What does a coil boot do?
In coil-on-plug and coil-near-plug systems, the coil boot forms the insulative path between the ignition coil and the spark plug, carrying high voltage while sealing out under-hood heat and moisture.
What are signs my coil boot may need replacing?
Cracked or degraded boots can cause arc-through, misfires, or hard starting. Diagnose the actual cause first, since these symptoms can also come from other ignition components.
What is the 900-P2101 coil boot made of?
It's constructed from high-temp silicone and reinforced materials designed to resist oil, fuel, and under-hood heat for durable high-voltage insulation.
Will this fit my vehicle?
It's a direct-fit replacement for the 2006 Saab 9-2X, 2004-2006 Subaru Baja, 2004-2010 Forester, 2004-2014 Impreza, 2005-2009 Legacy, and 2005-2009 Outback. Check the "Vehicles it fits" section to confirm.
Should I replace all the boots at once?
This is an OE-replacement coil boot. During an ignition tune-up, replacing the boots on all cylinders together helps keep spark insulation consistent across the engine.
