P0300 Toyota Highlander
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 Toyota Highlander 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 Toyota Highlander.
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 Toyota Highlander.
Common Causes on Toyota Highlander
- Ignition coil degradation on 2.5L four-cylinder or 3.5L V6 in RAV4/Highlander
- Spark plug wear beyond service interval on 3.5L V6 causing intermittent misfires
- Carbon buildup on intake valves on direct-injection-only 2.5L engines in certain RAV4 years
- Fuel injector fouling from ethanol-blend fuel causing lean misfire on individual cylinders
- EGR system deposit buildup causing uneven exhaust gas recirculation across cylinders
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
Notes for Toyota Highlander
Highlander and RAV4 with the 3.5L V6 use port injection which keeps intake valves cleaner.