Geely Fault Code

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P0300

Rough Low Idle / Flashing Check Engine

Variant 1

System

Ignition / Fuel

Symptom

Rough Low Idle / Flashing Check Engine

Diagnosis & fix steps

LOGIC: Random Multiple Cylinder Misfire. ACTION: Inspect pencil ignition coils for white carbon tracking along rubber boots. Check spark plug gap (spec: 0.8–0.9 mm); clean varnished fuel injector tips with an ultrasonic bath.

Red Seal field insights

Ethanol Gumming: E10 pump gas forms sticky lacquer on low-pressure multi-port injector nozzles when machines sit idle in high humidity, causing uneven spray patterns.

Variant 2

System

Ignition / Fuel

Symptom

Rough Idle / Flashing Check Engine

Diagnosis & fix steps

LOGIC: Random / Multiple Cylinder Misfire Detected. ACTION: Remove direct-injection pencil coils; check spark plug porcelain insulators for carbon tracking. Test high-pressure fuel delivery under load; verify intake valve backsides are not choked with dry PCV carbon crust.

Red Seal field insights

Direct Injection Carbon: Direct-injected 1.5T heads develop heavy carbon build-up on the tulip of the intake valves by 50,000 km, causing air tumbling turbulence and misfires at low idle.

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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