how to fix GMC Sierra T1XX (2019-Present) fog lights not working

GMC Sierra T1XX (2019-Present)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

4 min read

627 words

Problem Statement

Learn how to diagnose and fix fog lights not working on GMC Sierra T1XX (2019-Present). Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Electrical

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems to prevent short circuits.

Symptoms

•Fog lights do not illuminate when activated
•Fog light indicator on the dashboard remains off
•No clicking sound from the fog light relay when the switch is activated
•Potential blown fuse for fog lights
•Dim or flickering fog lights when activated (if intermittently working)

Diagnostic Steps

1
Inspect the fog light bulbs for any signs of damage or burnout.
2
Check the fog light fuse in the fuse box for any signs of burnout.
3
Use an OBD-II scanner to check for any error codes related to the lighting system.
4
Test the fog light switch for proper operation using a multimeter.
5
Inspect the wiring harness and connectors for corrosion or damage.
6
Check the fog light relay operation by swapping it with a similar relay in the fuse box.

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

•Socket set
•Multimeter
•OBD-II scanner
•Fuse puller or pliers

Parts Required

•Fog light bulbs (if burnt)
•Fog light fuse (if blown)
•Fog light switch (if faulty)

Related Faults

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Diagnostic Steps

1
Inspect the fog light bulbs for any signs of damage or burnout.
2
Check the fog light fuse in the fuse box for any signs of burnout.
3
Use an OBD-II scanner to check for any error codes related to the lighting system.
4
Test the fog light switch for proper operation using a multimeter.
5
Inspect the wiring harness and connectors for corrosion or damage.
6
Check the fog light relay operation by swapping it with a similar relay in the fuse box.

Solution

1. Preparation

Gather tools and parts required for the repair.
Disconnect the negative terminal from the battery to ensure safety.
Tools Required: Socket set, multimeter, OBD-II scanner.

2. Inspect and Replace Bulbs

Remove the fog light assembly from the front bumper by unscrewing the retaining screws.
- Sub-steps:
  - Use a socket wrench to remove screws.
  - Carefully pull the fog light assembly out.
Check the bulb condition; if burnt, replace with new bulbs (ensure correct type).
- Sub-steps:
  - Twist the bulb socket counterclockwise to remove the bulb.
  - Insert the new bulb and twist clockwise to secure.

3. Check and Replace Fuse

Locate the fuse box under the dashboard or hood.
- Sub-steps:
  - Remove the cover and identify the fog light fuse (refer to the diagram on the fuse box cover).
Inspect the fog light fuse; if blown, replace it with a fuse of the same rating (usually 15A).
- Sub-steps:
  - Pull the blown fuse with a fuse puller or pliers.
  - Insert the new fuse into the same slot.

4. Test Fog Light Switch

Use a multimeter to check for continuity on the fog light switch.
- Sub-steps:
  - Remove the switch from the dashboard.
  - Set the multimeter to continuity mode and test the switch terminals.
  - If no continuity is found, replace the fog light switch.

5. Inspect Wiring and Relay

Visually inspect the wiring harness for signs of wear, corrosion, or disconnection.
- Sub-steps:
  - Check connectors for tightness and clean contacts if necessary.
Swap the fog light relay with another relay (such as the horn relay) to test functionality.
- Sub-steps:
  - Remove the fog light relay from the fuse box.
  - Insert the equivalent relay from another circuit and test the fog lights.