how to diagnose P0301 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, and vacuum gauge.
• Disconnect the battery to ensure safety while working on electrical components.

2. Replace Spark Plug and Ignition Coil (if faulty)

1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the ignition coil connector and remove the ignition coil from Cylinder 1.
3. Remove the spark plug using a spark plug socket and inspect it for wear or damage.
4. Install a new spark plug, ensuring it is gapped correctly according to manufacturer specifications (typically 0.043 inches).
5. Install the new ignition coil and reconnect the connector, securing it properly.

3. Test and Replace Fuel Injector (if needed)

1. Disconnect the fuel injector connector for Cylinder 1.
2. Use a multimeter to check for proper voltage at the injector connector while cranking the engine.
3. If there is no voltage, inspect the wiring and connection to the ECM; repair as necessary.
4. If the injector is faulty, remove it and replace it with a new one, applying a small amount of engine oil to the O-ring for better sealing.

4. Conduct Compression Test

1. Remove the spark plug for Cylinder 1.
2. Insert the compression tester into the spark plug hole and crank the engine for a few seconds.
3. Record the compression reading; compare it with the specifications for the engine (typically around 180 psi).
4. If the compression is low, further diagnosis may be needed to check for valve issues or head gasket failure.