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

GMC Sierra T1XX (2019-Present)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

3 min read

556 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 steps and repair instructions.

Affected Component

Electrical

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect battery before working on electrical systems to avoid shocks or shorts.

Symptoms

•Fog lights do not illuminate when activated
•Fog light indicator on the dashboard is off
•Possible clicking sound when fog lights are turned on
•Other exterior lights functioning normally
•No blown fuses for the fog light circuit

Diagnostic Steps

1
Verify if the fog light switch is functioning by checking for continuity using a multimeter.
2
Inspect the fog light bulbs for any signs of damage or burnout.
3
Check the fog light fuse in the fuse box for continuity and replace if necessary.
4
Examine the wiring harness for any visible damage or disconnection.
5
Test the fog light relay by swapping it with a similar relay in the fuse box.
6
Use an OBD-II scanner to check for any related error codes that could indicate a wiring issue.

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
•Socket set
•Fuse pullers or pliers

Parts Required

•Fog light bulbs
•Replacement fuse (if necessary)
•Fog light relay (if faulty)

Related Faults

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Diagnostic Steps

1
Verify if the fog light switch is functioning by checking for continuity using a multimeter.
2
Inspect the fog light bulbs for any signs of damage or burnout.
3
Check the fog light fuse in the fuse box for continuity and replace if necessary.
4
Examine the wiring harness for any visible damage or disconnection.
5
Test the fog light relay by swapping it with a similar relay in the fuse box.
6
Use an OBD-II scanner to check for any related error codes that could indicate a wiring issue.

Solution

1. Preparation

Gather tools: multimeter, socket set, new fog light bulbs, replacement fuse if necessary.
Ensure the vehicle is parked on a flat surface and the engine is off.
Disconnect the negative terminal of the battery to ensure safety.

2. Inspect and Replace Bulbs

Sub-steps:
1. Access the fog light assembly by removing the underbody cover if applicable.
2. Disconnect the electrical connector from the fog light bulb.
3. Remove the bulb by turning it counterclockwise and pulling it out of the socket.
4. Insert a new bulb by aligning it properly and turning it clockwise to secure.
5. Reconnect the electrical connector.

3. Check and Replace Fuse

Sub-steps:
1. Locate the fuse box (usually under the dashboard or in the engine compartment).
2. Identify the fog light fuse using the diagram on the fuse box cover.
3. Pull the fuse out using fuse pullers or pliers.
4. Check the fuse for continuity; replace it if blown with a fuse of the same amperage.
5. Reinsert the fuse into the fuse box.

4. Inspect Wiring and Relay

Sub-steps:
1. Visually inspect the wiring harness leading to the fog lights for fraying or breaks.
2. Use a multimeter to test for voltage at the fog light connector while the fog lights are activated.
3. If no voltage is present, locate the fog light relay in the fuse box.
4. Remove the relay and test it by swapping it with another relay of the same type.
5. If the fog lights work with the swapped relay, replace the faulty relay.