how to diagnose P0301 code on my Toyota RAV4 XA50 (2019-2024)

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, multimeter, compression tester, fuel injector cleaner.
• Ensure the engine is cool and the vehicle is on a flat surface.
• Disconnect the negative battery terminal to prevent electrical shocks.

2. Inspect and Replace Ignition Components

1. Remove the engine cover if applicable using a socket set.
2. Remove the ignition coil for cylinder 1:
   • Disconnect the electrical connector.
   • Remove mounting bolts and lift the coil out.
3. Inspect the spark plug:
   • Remove the spark plug using a spark plug socket.
   • Check for wear, carbon buildup, or damage.
4. Replace the spark plug if necessary (recommended gap: 0.043 inches).
5. Reinstall the ignition coil (torque to 7.2 ft-lbs) and reconnect the electrical connector.

3. Check and Clean Fuel Injector

1. Locate the fuel injector for cylinder 1.
2. Disconnect the fuel injector electrical connector.
3. Use a fuel injector cleaner and follow the manufacturer's instructions to clean the injector.
4. Reconnect the fuel injector and ensure it is seated properly.

4. Compression Test

1. Remove the spark plug from cylinder 1.
2. Insert the compression tester into the spark plug hole.
3. Crank the engine for several seconds and read the compression values:
   • Minimum acceptable compression is typically 125 psi; consult the service manual for exact specifications.
4. If compression is low, further investigation of engine internals may be required.

5. Inspect for Vacuum Leaks

1. With the engine running, use a spray bottle with soapy water to check for bubbles around vacuum hoses and the intake manifold.
2. Repair or replace any leaking hoses or gaskets found during inspection.