What should I do if the engine starts but dies immediately in my 2023 Highlander?

If your 2023 Toyota Highlander starts but dies immediately, this issue can be attributed to several potential causes. Below is a structured approach to diagnosing and addressing this problem.

Step 1: Check for Diagnostic Trouble Codes (DTC)

Tools Required:

• OBD-II scanner

Instructions:

1. Connect the OBD-II scanner to the vehicle’s diagnostic port (usually located under the dashboard near the driver's side).
2. Turn the ignition to the "ON" position without starting the engine.
3. Follow the instructions on the scanner to read any stored or pending trouble codes.
4. Take note of any codes and look them up for further insights into the issue.

Step 2: Inspect Fuel Supply

Tools Required:

• Fuel pressure gauge
• Basic hand tools (screwdrivers, wrenches)

Instructions:

1. Locate the fuel rail on the engine.
2. Connect the fuel pressure gauge to the Schrader valve on the fuel rail.
3. Turn the ignition to the "ON" position (do not start the engine) and check the pressure reading. Compare it to the manufacturer’s specifications (usually around 50-60 psi for most models).
4. If the pressure is low, check for fuel pump operation by listening for the pump to engage when the ignition is turned on.
5. If the pump does not engage, check the fuel pump fuse and relay.
6. If the fuse and relay are good, the fuel pump may need replacement.

Step 3: Check for Air Intake Issues

Tools Required:

• Basic hand tools (screwdrivers, wrenches)

Instructions:

1. Inspect the air intake system for any obstructions (e.g., dirt, debris).
2. Check the air filter for cleanliness; replace it if it is clogged.
3. Ensure the Mass Air Flow (MAF) sensor is clean and functioning. If necessary, clean it with MAF sensor cleaner.

Step 4: Assess Spark and Ignition System

Tools Required:

• Spark plug socket
• Multimeter (for ignition coil testing)

Instructions:

1. Remove one spark plug and inspect it for wear or fouling. Replace if necessary.
2. Reconnect the ignition coil and use a multimeter to check for proper voltage at the coil when the engine is cranked.
3. If there is no spark, the ignition coil or crankshaft position sensor may be faulty.

Repair Instructions

Repairing Fuel System Issues

1. If the fuel pump is faulty, replace it by:
   • Disconnecting the battery.
   • Removing the rear seat or accessing the fuel pump from underneath the vehicle.
   • Disconnecting the fuel lines and electrical connections.
   • Removing the fuel pump assembly and installing the new pump.
   • Reconnecting everything and testing the fuel pressure again.

Repairing Air Intake Issues

1. Replace the air filter if necessary.
2. If the MAF sensor is faulty, replace it by:
   • Disconnecting the electrical connector.
   • Unscrewing the sensor from the intake tube and installing a new sensor.

Repairing Ignition System Issues

1. If the ignition coil is bad, replace it by:
   • Disconnecting the battery.
   • Removing the ignition coil from its mount.
   • Installing a new coil and reconnecting the battery.

Final Verification

1. After performing repairs, attempt to start the engine again.
2. Monitor for any unusual sounds or warning lights.
3. If the engine runs smoothly, take the vehicle for a short test drive to ensure the issue is resolved.

Conclusion

If the issue persists after these steps, further investigation may be necessary, potentially involving more advanced diagnostics with a professional technician. Always refer to the vehicle’s service manual for specific procedures and specifications.