P0300 on Toyota Grand Highlander: Fix & DLC Location
Factory diagnostic troubleshooting wire for fault code P0300 (P0300: Random or Multiple Cylinder Misfire Detected) specifically on the Toyota Grand Highlander (2024–2026, 2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD).
1. Symptoms of P0300 on Toyota Grand Highlander
When the Engine Control Module (ECM/PCM) on your Toyota Grand Highlander (2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD) logs fault code P0300, drivers commonly observe:
2. Most Likely Causes on Toyota Grand Highlander
Historical warranty claims and technical repair bulletins for Toyota Grand Highlander point to the following failure distribution:
3. Step-by-Step DIY Repair Guide for Toyota Grand Highlander
Plug a handheld OBD-II scanner into the 16-pin port under the dashboard. Check if specific cylinder codes like P0301 (Cylinder 1) or P0304 (Cylinder 4) accompany P0300. on the Toyota Grand Highlander equipped with 2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD.
Remove the ignition coils, use a spark plug socket with ratchet to unthread spark plugs. Inspect electrode tips for carbon buildup, oil fouling, or burnt gaps. Replace with OEM iridium plugs gapped to spec. on the Toyota Grand Highlander equipped with 2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD.
Perform an ignition swap test: Swap coil from a suspected misfiring cylinder to an adjacent cylinder. Clear codes and re-scan. If the misfire moves, replace the faulty coil. on the Toyota Grand Highlander equipped with 2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD.
Inspect PCV hoses, intake boot, and vacuum lines for cracking or hissing sounds while engine idles. Smoke test the intake if necessary. on the Toyota Grand Highlander equipped with 2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD.
Add a bottle of premium fuel injector cleaner (e.g. Chevron Techron). Clear the OBD-II codes with your scanner and take the car on a 15-minute drive cycle to confirm readiness monitors reset. on the Toyota Grand Highlander equipped with 2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD.
Other Common Fault Codes on Toyota Grand Highlander
Frequently diagnosed powertrain, emissions, and sensor trouble codes logged on the Toyota Grand Highlander:
4. Toyota Grand Highlander P0300 FAQs
What causes code P0300 to trigger on a Toyota Grand Highlander?
On the Toyota Grand Highlander (2.4L Turbo / 2.5L Hybrid / Hybrid MAX 362HP Turbo AWD), P0300 is most frequently caused by Worn or fouled spark plugs and damaged spark plug wires or Failing ignition coils or coil packs.
Where is the OBD-II port located on my Toyota Grand Highlander?
On the Toyota Grand Highlander, the 16-pin DLC diagnostic connector is located Driver side lower knee panel above dead pedal. Plug in any standard OBD-II scanner with the ignition in the ON position to read freeze-frame parameters.
Can I safely drive my Toyota Grand Highlander with code P0300?
No. Driving with a flashing check engine light causes irreversible catalytic converter damage. Given that P0300 carries a Critical severity rating, we advise avoiding heavy towing or aggressive throttle inputs until sensor readings are verified.