what causes the check engine light to come on in my Toyota RAV4

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, multimeter, fuel pressure gauge, torque wrench.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to ensure safety while working on electrical components.

2. Address Error Codes

• Connect the OBD-II scanner to the vehicle's diagnostic port.
• Record any trouble codes, then clear them from the system.
• Start the engine and see if the check engine light reappears.

3. Inspect and Replace Components

A. Gas Cap

• Remove the gas cap and inspect for cracks or damage.
• If damaged, replace it with a new gas cap. Ensure it clicks securely when reinstalled.

B. Air Filter

• Locate the air filter housing and remove it by unscrewing or unclipping.
• Remove the old air filter and replace it with a new one, ensuring it fits properly.

C. Spark Plugs and Ignition Coils

• Remove the engine cover (if applicable) to access the spark plugs.
• Using a socket, remove spark plugs, inspecting for wear or carbon buildup.
• Replace with new spark plugs, torquing to the manufacturer's specification.
• Inspect ignition coils for damage; replace if necessary.

D. Vacuum Leaks

• Inspect all vacuum lines for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks.
• Replace any damaged hoses or connections.

4. Fuel Pressure Check

• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "On" position (without starting the engine) and check the pressure reading against manufacturer specifications.
• If pressure is low, inspect the fuel pump and filter for issues and replace as necessary.