Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSUBARU2016LEGACY 2.5IREPAIR AND DIAGNOSISENGINE MECHANICALENGINE LUBRICATION SYSTEM (H4DO)ENGINE LUBRICATION SYSTEM TROUBLE IN GENERALINSPECTION
2016 Subaru Legacy 2.5i
Engine Lubrication System Trouble in General: Inspection
2016 Subaru Legacy 2.5iSECTION Inspection
Before performing diagnostics, make sure that the engine oil level is correct and no oil leakage exists.
| Trouble | Possible cause | Corrective action |
|---|---|---|
| Warning light remains ON. | a. Oil pressure switch failure | |
| • Cracked diaphragm or oil leakage within switch | Replace. | |
| • Broken spring or seized contacts | Replace. | |
| b. Low oil pressure | ||
| • Clogging of oil filter | Replace. | |
| • Malfunction of oil by-pass valve in oil filter | Replace. | |
| • Malfunction of oil relief valve in oil pump | Replace. | |
| • Clogged oil passage | Clean. | |
| < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. > Excessive tip clearance and side clearance of oil pump rotor | Replace. | |
| • Clogged oil strainer or broken pipe | Clean or replace. | |
| c. No oil pressure | ||
| • Insufficient engine oil (degradation, etc.) | Replace. | |
| • Broken pipe of oil strainer | Replace. | |
| • Stuck oil pump rotor | Replace. | |
| Warning light does not illuminate. | a. Malfunction of combination meter | Replace. |
| b. Poor contact of switch contact points | Replace. | |
| c. Disconnection of wiring | Repair. | |
| Warning light flickers momentarily. | a. Defective terminal contact | Repair. |
| b. Defective wiring harness | Repair. | |
| c. Oil pressure switch failure | ||
| • Cracked diaphragm or oil leakage within switch | Replace. | |
| • Broken spring or seized contacts | Replace. | |
| d. Low oil pressure | ||
| • Clogging of oil filter | Replace. | |
| • Malfunction of oil by-pass valve in oil filter | Replace. | |
| • Malfunction of oil relief valve in oil pump | Replace. | |
| • Clogged oil passage | Clean. | |
| • Excessive tip clearance and side clearance of oil pump rotor | Replace. | |
| • Clogged oil strainer or broken pipe | Clean or replace. | |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.