Subaru check engine codes
Overview
Subaru boxer engines commonly show catalytic converter, lean, thermostat, and EVAP codes. Older EJ25 engines are well documented for head gasket leaks.
Codes notably common on Subaru
- P0420 Catalyst System Efficiency Below Threshold (Bank 1) · Subaru notes
- P0171 System Too Lean (Bank 1) · Subaru notes
- P0300 Random or Multiple Cylinder Misfire Detected · Subaru notes
- P0128 Coolant Thermostat (Coolant Temperature Below Regulating Temperature)
- P0456 Evaporative Emission System Very Small Leak Detected
Subaru specific notes
- Older EJ25 2.5 liter engines are well documented for head gasket leaks, most often external oil or coolant seepage. Left alone, leaks can lead to coolant loss and overheating, which means stop driving.
- Boxer engines place spark plugs low on each side, so plug and coil access takes longer than on inline engines.
Owner's manuals
Official Subaru owner's manual / owner portal (manufacturer site; we do not host copies).
Repair manuals
Step-by-step service manuals for Subaru with torque specs and wiring diagrams:
Haynes manuals for Subaru Chilton manuals
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Recall lookup
Check open Subaru recalls with your VIN at the NHTSA recall lookup.
Sources
- https://www.felpro.com/technical/tecblogs/sealing-subaru-2-5l-engines.html
- https://www.nhtsa.gov/recalls
Sources checked October 2026. Bulletins apply only to the models and years they list.
All other codes
These work the same on Subaru as on any vehicle:
P0430 P0301 P0302 P0303 P0304 P0174 P0440 P0442 P0455 P0135 P0141 P0101 P0299 P2135 P0401