Subaru Fault Code

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P0300

Engine Shudder / Flashing MIL

System

Ignition / Fuel

Symptom

Engine Shudder / Flashing MIL

Diagnosis & fix steps

LOGIC: Random / Multiple Cylinder Misfire Detected. ACTION: Inspect spark plug wells for engine oil pooling from leaking spark plug tube seals. Check direct-injection ignition coil boots for white carbon tracking; inspect the engine grounding straps on the cylinder heads.

Red Seal field insights

Oil-Soaked Coils: Boxer engine cylinder heads sit flat, allowing leaking valve cover tube seals to submerge the lower coil boots and spark plugs in engine oil, causing spark flashover.

Same code keeps coming back?

That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.

Book an uptime review

Read before you touch anything

  • This is general reference information, not a repair manual. It is for trained, qualified technicians.
  • Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
  • Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
  • You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
  • Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.

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