What issues might cause the automatic headlights to malfunction in a 2021 Toyota Highlander?

Toyota Highlander Fourth Generation (2020-present)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

584 words

Problem Statement

Learn about the symptoms, potential causes, and diagnostic steps for automatic headlights malfunction in the 2021 Toyota Highlander.

Affected Component

automatic headlights

Estimated Time

2-4 hours

Symptoms

•Headlights do not turn on automatically at dusk or in low-light conditions.
•Headlights remain on during the day when they should turn off.
•Dashboard indicator for headlights remains illuminated or shows a warning.
•Inconsistent operation of headlights (turning on/off unexpectedly).

Diagnostic Steps

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

•Flashlight
•multimeter
•wiring diagram
•basic hand tools
•relay tester
•OBD-II scanner

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Solution

Automatic Headlights Malfunction in a 2021 Toyota Highlander

Symptoms:

Headlights do not turn on automatically at dusk or in low-light conditions.
Headlights remain on during the day when they should turn off.
Dashboard indicator for headlights remains illuminated or shows a warning.
Inconsistent operation of headlights (turning on/off unexpectedly).

Potential Causes:

Faulty Light Sensor
Wiring Issues
Faulty Headlight Relay
Malfunctioning Body Control Module (BCM)
Software Glitches
Burnt Out Bulbs or Fuses

Step 1: Visual Inspection

Tools Required: Flashlight, multimeter.
Check the headlights and taillights for any burnt out bulbs.
Inspect fuses related to the headlight system using the owner's manual for fuse locations.

Step 2: Test the Light Sensor

Tools Required: Multimeter.
Locate the light sensor, usually found on the dashboard near the windshield.
Measure the resistance or voltage output of the sensor in different lighting conditions (dark vs. light). Refer to the service manual for specifications.

Step 3: Check Wiring and Connectors

Tools Required: Wiring diagram, multimeter, and basic hand tools.
Inspect the wiring harness connected to the light sensor and the headlight relay for any signs of wear, corrosion, or disconnection.
Use the multimeter to check for continuity in the wiring.

Step 4: Test the Headlight Relay

Tools Required: Relay tester or multimeter.
Locate the headlight relay in the fuse box.
Swap it with a similar relay (if available) to check if the headlights operate correctly.
If using a multimeter, test for voltage at the relay terminals when the headlights are activated.

Step 5: Scan for Diagnostic Trouble Codes (DTCs)

Tools Required: OBD-II scanner.
Connect the OBD-II scanner to the vehicle’s port and check for any trouble codes related to the lighting or BCM.
Make note of any codes and consult the service manual for further troubleshooting based on the specific codes retrieved.

Repair Instructions:

Repairing or Replacing Components

1. Replace the Light Sensor:

Disconnect the battery.
Remove the sensor from its housing (may require prying or unscrewing).
Install the new sensor and reconnect the battery.
Test the headlights to ensure they operate correctly.

2. Repair Wiring Issues:

If damaged wires are found, cut out the damaged section and splice in new wiring.
Use heat shrink tubing and electrical tape to ensure all connections are insulated and secure.
Test the system again.

3. Replace the Headlight Relay:

If testing confirmed the relay is faulty, remove the old relay from the fuse box.
Install the new relay in the same position.
Reconnect the battery and test the headlights.

4. Update or Replace BCM:

If all else fails and the BCM is suspected of malfunctioning, consult with a professional for reprogramming or replacement.
This process usually requires specialized equipment.

5. Software Update:

Check with a Toyota dealership for any software updates available for the BCM that may resolve known issues.
Follow dealership instructions for updating the software.

Final Testing:

After performing repairs, conduct a thorough test of the automatic headlights:

Test in various lighting conditions (daytime and nighttime).
Ensure that the headlights turn on and off automatically as designed.
Verify that dashboard indicators function correctly.

If issues persist, further diagnostics may be required or a consultation with a professional technician or dealership may be necessary.