why does my Toyota Highlander Third Generation (2014-2019) check engine light keep coming on

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the vehicle battery to ensure safety while working on electrical components.

2. Address Faulty Components

A. Replace Faulty Oxygen Sensors

• Locate the oxygen sensors (upstream and downstream).
• Use an O2 sensor socket to remove the old sensors.
• Apply anti-seize compound on the threads of the new sensors before installation.
• Install the new sensors and reconnect the wiring harness.

B. Replace Spark Plugs and Ignition Coils (if needed)

• Remove the engine cover (if applicable).
• Disconnect the electrical connectors from the ignition coils.
• Unbolt and remove the ignition coils.
• Remove old spark plugs using a spark plug socket.
• Install new spark plugs (torque to manufacturer specifications).
• Reinstall ignition coils and reconnect electrical connectors.

C. Repair or Replace Vacuum Hoses

• Inspect all visible vacuum hoses for cracks or disconnections.
• Replace any damaged hoses with OEM parts, ensuring a secure fit.

3. Clear Error Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear the error codes and reset the check engine light.