What causes P0300 on a Mazda Cx-5?

Common causes of P0300 on Mazda Cx-5: Ignition coil failure on Skyactiv-G 2.5L or 2.0L four-cylinder (CX-5/CX-50/Mazda3/CX-30); Spark plug electrode erosion from high compression ratio (13:1) of Skyactiv-G engine; Carbon buildup on intake valves from GDI on Skyactiv-G 2.5L direct injection models; Fuel injector tip fouling from carbon deposits on high-compression GDI system; PCV valve failure causing crankcase pressure and oil mist contaminating spark plugs.

P0300

P0300 Mazda Cx-5

Q: How much does it cost to fix P0300 on a Mazda Cx-5?

Fixes for P0300 on Mazda Cx-5 include: Replace all ignition coils with Denso OE and new NGK ILKAR7L11 iridium spark plugs, Replace spark plugs at 50k miles instead of 75k due to high compression ratio wear, Perform intake valve cleaning using walnut shell media on GDI-only Skyactiv-G engines, Clean fuel injectors with professional ultrasonic service or replace with Mazda OE, Replace PCV valve and clean valve cover ventilation passages.

Random/Multiple Cylinder Misfire Detected · Powertrain Code · High · Repair: Easy

What is P0300?

The ECM has detected misfires occurring in multiple or random cylinders. Common causes include worn spark plugs, faulty ignition coils, vacuum leaks, low fuel pressure, or a failing catalytic converter.

When the Mazda Cx-5 triggers code P0300 (random/multiple cylinder misfire detected), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the Mazda Cx-5.

This repair is rated easy, meaning basic tools, no lift needed.

Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Mazda Cx-5.

Common Causes on Mazda Cx-5

Ignition coil failure on Skyactiv-G 2.5L or 2.0L four-cylinder (CX-5/CX-50/Mazda3/CX-30)
Spark plug electrode erosion from high compression ratio (13:1) of Skyactiv-G engine
Carbon buildup on intake valves from GDI on Skyactiv-G 2.5L direct injection models
Fuel injector tip fouling from carbon deposits on high-compression GDI system
PCV valve failure causing crankcase pressure and oil mist contaminating spark plugs

Symptoms

Rough idle with noticeable engine vibration
Engine shaking or stumbling under load
Loss of power during acceleration
Check engine light flashing intermittently
Poor fuel economy
Hesitation or stumble on acceleration

Recommended Fixes

Replace all ignition coils with Denso OE and new NGK ILKAR7L11 iridium spark plugs

Replace spark plugs at 50k miles instead of 75k due to high compression ratio wear

Perform intake valve cleaning using walnut shell media on GDI-only Skyactiv-G engines

Clean fuel injectors with professional ultrasonic service or replace with Mazda OE

Replace PCV valve and clean valve cover ventilation passages

Notes for Mazda Cx-5

Skyactiv-G high compression ratio (13:1) demands premium ignition components for reliable combustion.

P0300 Mazda Cx-5

What is P0300?

Common Causes on Mazda Cx-5

Symptoms

Notes for Mazda Cx-5

Check Mazda Cx-5 Specs