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What should I check if my 2020 Toyota Highlander's headlights are flickering? - Toyota Highlander
Home/Cars/Toyota/Highlander/Fourth Generation (2020-present)/What should I check if my 2020 Toyota Highlander's headlights are flickering?

What should I check if my 2020 Toyota Highlander's headlights are flickering?

Toyota Highlander Fourth Generation (2020-present)

Error Codes
medium
Difficulty
medium
Severity
Navigation
ProblemSymptomsDiagnosisSolution
ProblemSymptomsDiagnosisSolution
4 min read
716 words

Problem Statement

Learn how to diagnose and fix flickering headlights on your 2020 Toyota Highlander with our step-by-step guide.

Affected Component
headlights

Symptoms

  • •flickering headlights
  • •dimming lights
  • •inconsistent brightness
  • •complete failure of headlights

Diagnostic Steps

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6

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

  • •Multimeter
  • •Wire brush or corrosion cleaner
  • •Socket set
  • •Screwdrivers (Phillips and flathead)
  • •Electrical contact cleaner
  • •Replacement headlight bulbs (if necessary)
  • •Headlight relay (if necessary)
  • •Battery terminal cleaner (if necessary)

Additional Information

Affected Component
headlights
Difficulty
medium
Severity
medium
Tools Required
8 items

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Possible Causes
  1. Faulty Headlight Bulbs - The bulbs may be reaching the end of their life or have internal defects.
  2. Loose Connections - Wiring or connectors may be loose, leading to intermittent power delivery.
  3. Faulty Headlight Relay - The relay responsible for powering the headlights may be malfunctioning.
  4. Weak Battery - A battery that is not delivering consistent voltage can cause flickering.
  5. Alternator Issues - A failing alternator can cause fluctuating voltage levels.
  6. Corroded Grounds - Poor grounding can lead to electrical issues, including flickering lights.
Tools Required
  • Multimeter
  • Wire brush or corrosion cleaner
  • Socket set
  • Screwdrivers (Phillips and flathead)
  • Electrical contact cleaner
  • Replacement headlight bulbs (if necessary)
  • Headlight relay (if necessary)
  • Battery terminal cleaner (if necessary)

Step 1: Check the Headlight Bulbs

  1. Turn on the headlights: Observe the flickering behavior.
  2. Inspect the bulbs: Remove the headlight assembly (if necessary) and check for any visible damage or blackening of the bulbs.
  3. Test the bulbs: If you have a spare bulb, replace one at a time to see if the flickering stops.

Step 2: Inspect Electrical Connections

  1. Turn off the vehicle: Ensure your Highlander is off before proceeding.
  2. Access the headlight connector: Remove the headlight assembly to access the wiring harness.
  3. Check for loose connections: Ensure the connectors are firmly seated. If loose, reseat them.
  4. Look for signs of corrosion: Clean any corrosion on the connectors using electrical contact cleaner or a wire brush.

Step 3: Test the Headlight Relay

  1. Locate the headlight relay: Refer to the owner’s manual for the location in the fuse box.
  2. Remove the relay: Pull it out carefully using your fingers or a pair of pliers.
  3. Test the relay: Use a multimeter set to the continuity mode. Check if the relay is functioning correctly by testing terminals for continuity when activated.

Step 4: Check the Battery

  1. Turn on the vehicle: Start your Highlander and let it idle.
  2. Test battery voltage: Using a multimeter, check the voltage across the battery terminals. It should read around 12.6 volts when off and about 13.7 to 14.7 volts when running.
  3. Inspect battery terminals: Clean any corrosion on the battery terminals with a battery terminal cleaner.

Step 5: Inspect the Alternator

  1. Check alternator output: With the engine running, use the multimeter to test the voltage at the battery terminals. If the voltage is inconsistent or below 13.7 volts, the alternator may be failing.
  2. Listen for unusual noises: A failing alternator may emit grinding or whining sounds.

Step 6: Check Ground Connections

  1. Inspect ground wires: Locate the ground connection for the headlights, typically found near the battery or on the chassis.
  2. Check for corrosion: Clean any corroded connections and ensure they are tightly fastened.
Repair Instructions

If the Bulbs are Faulty:

  1. Replace the bulbs: Remove the old bulbs and install new ones by reversing the removal process.
  2. Test the headlights: After replacing, check if the flickering persists.

If Connections are Loose or Corroded:

  1. Reconnect and clean: Tighten any loose connections and clean corroded ones.
  2. Test headlights: Ensure the flickering has stopped.

If the Relay is Faulty:

  1. Replace the headlight relay: Install a new relay by reversing the removal process.
  2. Test headlights: Check for consistent light output.

If the Battery or Alternator is Faulty:

  1. Replace the battery if it is weak or not holding a charge.
  2. Replace the alternator if the output is inconsistent.
  3. Test the headlights: Ensure flickering is resolved after replacement.

If Ground Connections are Faulty:

  1. Clean and reconnect: Ensure that all ground connections are clean and secure.
  2. Test headlights: Check for flickering issues.
Conclusion

After following these diagnostic steps and performing the necessary repairs, the flickering headlights should be resolved. If the issue persists, further investigation into the vehicle’s electrical system may be required, or consulting a professional technician may be advisable.