What causes fault code P0300?

• Most likely: Worn out spark plugs or incorrect gap • Likely: Faulty ignition coils (COP) or ignition wires • Possible: Vacuum leak (intake manifold gasket or hoses) causing lean condition • Possible: Low fuel pressure or clogged fuel filter • Rare: Defective EGR valve stuck open • Rare: Internal engine mechanical problem (low compression or worn camshaft lobes)

Powertrain (Engine & Gearbox)Standard EOBD

P0300 - Random or Multiple Cylinder Misfire Detected

Q: What are the symptoms of fault code P0300?

• Check engine light (MIL) illumination or flashing • Engine hesitation or jerking during acceleration • Rough or unstable idle • Increased fuel consumption • Smell of raw fuel from the exhaust • Vehicle fails emissions test

Q: How do you fix fault code P0300?

STEP 1: Inspect spark plugs for wear or fouling. Check ignition wires/boots for carbon tracking or cracks. STEP 2: Use a scan tool to monitor 'Misfire Counters' in live data. Identify if specific cylinders are contributing more than others. STEP 3: Test fuel pressure (typically 45-65 PSI) and check for a clogged fuel filter. STEP 4: Check Short Term and Long Term Fuel Trims. If positive trims are high, perform a smoke test to find intake vacuum leaks. STEP 5: Perform a compression test or cylinder leak-down test if mechanical failure is suspected.

Last updated:1 February 2026

Related:Spark Plugs, Ignition Coils, Crankshaft Position Sensor, Fuel Injectors, MAF Sensor, Insugspackning / Intake Gasket

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

P0304

Cylinder 4 Misfire Detected

Technical Description

P0300 is an OBD-II generic code indicating that the Engine Control Unit (ECU) has detected that one or more cylinders are not firing properly. The ECU monitors the crankshaft position sensor (CKP) signal for variations in rotational speed. If a cylinder fails to contribute to the crankshaft speed, a misfire event is logged. When misfires are random and not limited to a single specific cylinder (which would trigger P0301-P0312), P0300 is stored. If the misfire rate is high enough to damage the catalytic converter, the MIL will flash.

Possible Causes

Worn out spark plugs or incorrect gap

Faulty ignition coils (COP) or ignition wires

Vacuum leak (intake manifold gasket or hoses) causing lean condition

Low fuel pressure or clogged fuel filter

Defective EGR valve stuck open

Internal engine mechanical problem (low compression or worn camshaft lobes)

Symptoms

Check engine light (MIL) illumination or flashing

Engine hesitation or jerking during acceleration

Rough or unstable idle

Increased fuel consumption

Smell of raw fuel from the exhaust

Vehicle fails emissions test

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P0300 - Random or Multiple Cylinder Misfire Detected

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Mechanic's Tip

Do you also have
other fault codes?

Berörda ECU-familjer

P0300 - Random or Multiple Cylinder Misfire Detected

Related Fault Codes

Technical Description

Possible Causes

Symptoms

Recommended Solution

Workflow

Mechanic's Tip

Do you also have other fault codes?

Berörda ECU-familjer

Do you also have
other fault codes?