why does my Toyota Highlander Third Generation (2014-2019) check engine light come on and off

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

573 words

Problem Statement

Learn how to diagnose and fix the intermittent check engine light issue in a 2014-2019 Toyota Highlander. Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Engine

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before performing any repairs.

Symptoms

•Check engine light illuminates and then turns off intermittently
•Possible rough idle or engine misfire
•Decreased fuel efficiency
•Unusual engine noises
•Emissions test failure (if applicable)

Diagnostic Steps

1
Scan the vehicle's onboard diagnostics (OBD-II) system for error codes using an OBD-II scanner.
2
Record any stored trouble codes and research their meanings.
3
Inspect the gas cap for proper sealing and any signs of damage.
4
Check for vacuum leaks in hoses and intake manifold.
5
Examine the condition of spark plugs and ignition coils.
6
Verify the functionality of the mass airflow sensor and oxygen sensors.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Torque wrench
•Multimeter
•Smoke tester (optional)

Parts Required

•Oxygen sensor (if applicable)
•Mass airflow sensor (if applicable)
•Spark plugs
•Ignition coils (if applicable)
•Vacuum hoses (if damaged)

Related Faults

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Diagnostic Steps

1
Scan the vehicle's onboard diagnostics (OBD-II) system for error codes using an OBD-II scanner.
2
Record any stored trouble codes and research their meanings.
3
Inspect the gas cap for proper sealing and any signs of damage.
4
Check for vacuum leaks in hoses and intake manifold.
5
Examine the condition of spark plugs and ignition coils.
6
Verify the functionality of the mass airflow sensor and oxygen sensors.

Solution

1. Preparation

Gather tools and parts.
Disconnect the negative battery terminal to reset the check engine light and ensure safety.
Tools Required: OBD-II scanner, socket set, torque wrench, multimeter.

2. Address Fault Codes

Sub-step 1: Based on the trouble codes retrieved, identify the specific component causing the issue (e.g., oxygen sensor, mass airflow sensor).
Sub-step 2: If an oxygen sensor code is present, replace the faulty sensor. For example, remove the old sensor using a wrench and install the new one, ensuring proper torque (typically 30 Nm or 22 lb-ft).
Sub-step 3: If the mass airflow sensor is faulty, disconnect the wiring harness, unbolt it, and replace it with a new unit. Reconnect the harness securely.

3. Inspect and Replace Spark Plugs

Sub-step 1: Remove the ignition coils by unscrewing them from the engine block.
Sub-step 2: Take out the old spark plugs using a spark plug socket.
Sub-step 3: Inspect the condition of the spark plugs; replace them if they show signs of wear or damage. Install new spark plugs, ensuring they are gapped according to the manufacturer's specifications (usually around 0.043 inches).
Sub-step 4: Reattach the ignition coils.

4. Check for Vacuum Leaks

Sub-step 1: Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
Sub-step 2: Use a smoke tester to identify any leaks if necessary. Repair or replace any defective hoses.

5. Reassemble and Reset

Sub-step 1: Reconnect the negative battery terminal.
Sub-step 2: Clear any stored error codes using the OBD-II scanner.
Sub-step 3: Test drive the vehicle to ensure the check engine light does not reappear.