my GMC Sierra T1XX (2019-Present) tail lights are not working, what could be wrong?

GMC Sierra T1XX (2019-Present)

Error Codes

1-3 hours

Time

medium

Difficulty

medium

Severity

4 min read

601 words

Problem Statement

Learn how to diagnose and fix non-working tail lights in GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Affected Component

Electrical

Estimated Time

1-3 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical components to avoid shock or short-circuiting.

Symptoms

•Tail lights do not illuminate when headlights are turned on
•Brake lights may also be non-functional
•No indicator lights on the dashboard for tail light failure
•Possible blown fuses related to the tail light circuit
•Dim or flickering tail lights when activated

Diagnostic Steps

1
Inspect the tail light bulbs for any signs of damage or burnout.
2
Check the fuse box for blown fuses related to tail lights and replace if necessary.
3
Use an OBD-II scanner to check for any diagnostic trouble codes related to the lighting system.
4
Verify the wiring connections at the tail light assembly for corrosion or loose connections.
5
Test the tail light circuit with a multimeter to check for voltage and ground continuity.
6
Inspect the vehicle's body control module (BCM) for any faults or issues.

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

•Screwdriver set
•Multimeter
•Pliers or fuse pullers
•Electrical cleaner

Parts Required

•Tail light bulbs (e.g., 1157)
•Fuses (as needed)

Related Faults

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Diagnostic Steps

1
Inspect the tail light bulbs for any signs of damage or burnout.
2
Check the fuse box for blown fuses related to tail lights and replace if necessary.
3
Use an OBD-II scanner to check for any diagnostic trouble codes related to the lighting system.
4
Verify the wiring connections at the tail light assembly for corrosion or loose connections.
5
Test the tail light circuit with a multimeter to check for voltage and ground continuity.
6
Inspect the vehicle's body control module (BCM) for any faults or issues.

Solution

1. Preparation

Gather tools and parts.
Ensure the vehicle is parked on a flat surface, and the engine is turned off.
Disconnect the battery to avoid electrical shock.

2. Replace Tail Light Bulbs

Sub-steps:
- Open the tailgate and access the tail light assembly.
- Remove the screws or clips securing the tail light assembly.
- Gently pull out the tail light assembly to access the bulb sockets.
- Twist the bulb sockets counterclockwise to remove them.
- Replace any burned-out bulbs with new ones of the same type (e.g., 1157 for dual filament).
- Reassemble the tail light assembly and secure it with screws or clips.

3. Check and Replace Fuses

Sub-steps:
- Locate the fuse box, usually found under the dashboard or in the engine compartment.
- Identify the fuse for the tail lights (refer to the owner's manual for the exact fuse location).
- Remove the fuse using fuse pullers or pliers.
- Inspect the fuse for continuity; replace it if it is blown with a fuse of the same amperage.

4. Repair Wiring Connections

Sub-steps:
- Inspect the wiring harness connected to the tail lights for any visible damage or corrosion.
- Clean any corroded connectors with electrical cleaner and a wire brush.
- Ensure all connections are tight and secure; repair or replace damaged wires as needed.

5. Test Tail Light Circuit

Sub-steps:
- Reconnect the battery and turn on the vehicle.
- Use a multimeter to check for voltage at the tail light connector while the headlights are on.
- If no voltage is present, trace the wiring back to the BCM and check for continuity.