2016-2020 Cadillac CT6 Trunk Sill Plate: Damage, Illumination Failure, and Replacement
This guide covers common damage, failure of the illuminated version, and how to replace the trunk sill plate on your 2016-2020 CT6.
- The main variations are the standard black plastic plate and the optional illuminated stainless steel plate (Part No. 84263852).
- The illuminated version is a simple, plug-and-play upgrade for any 2016-2020 CT6.
- When buying a used plate, the most important things to check are that the mounting clips on the back are intact and, for illuminated versions, that the light is functional.
- Replacement is an easy DIY job requiring only basic trim tools and a socket wrench, with a torque of 20 Nm (15 lb-ft) for the cargo loops.
Symptoms of a Failing Trunk Sill Plate
Since the trunk sill plate is largely a cosmetic and protective part, "failure" relates to physical damage or, on upgraded models, electrical issues.
Cosmetic Damage
The most common issue is visible wear and tear from use. Look for:
- Scratches and Scuffs: Caused by dragging luggage, boxes, or other items over the sill.
- Cracks or Gouges: Resulting from impacts with heavy or sharp objects.
- Broken or Loose Fit: The plastic or metal clips that hold the sill plate in place can break over time, causing the plate to become loose, rattle, or lift up at the edges.
Illumination Failure (Upgraded Models)
The optional illuminated sill plate can experience electrical failures. Symptoms include:
- Light Not Turning On: The plate fails to illuminate when the trunk is opened. This could be due to a failed LED element within the plate or a wiring connection issue.
- Flickering or Intermittent Light: The light may flicker or work sporadically, often indicating a loose electrical connector or a failing internal component. Since the plate daisy-chains off the main trunk light, a problem with that circuit could also be the cause.
Part Variants and Compatibility
For the 2016-2020 Cadillac CT6, there are two primary versions of the trunk sill plate. Compatibility is determined by the feature, not the engine size.
- Standard Sill Plate: A non-illuminated, typically black plastic trim piece found on most models.
- Illuminated Sill Plate: An accessory or feature on higher trims, this plate is made with stainless steel and plastic, and it lights up when the trunk opens. It is a direct, plug-and-play upgrade for any CT6 model.
| Part | OEM Part Number(s) | Notes |
|---|---|---|
| Illuminated Trunk Sill Plate | 84263852 (Current), 23506072, 84162549 (Superseded) | This is the stainless steel, illuminated accessory version. It operates like a dome light, turning on when the trunk opens. It is a popular upgrade. |
| Standard Sill Plate | (Varies by specific vehicle build) | This is the basic, non-lit plastic version. Part number is best verified by VIN. |
Warning: The part numbers 23344069, 23349886, 23349888, 23349889, and 84005074 are often mis-cataloged but actually refer to the vehicle's Air Cleaner Housing for various engines, not the trunk sill plate. Always use the part numbers listed in the table above for the trunk sill plate.
Buying a Used Trunk Sill Plate
A used OEM sill plate is an excellent value, especially compared to the high cost of a new illuminated version. However, inspect it carefully before purchasing.
What to Check:
- Inspect for Cracks: Check the entire surface, especially around the edges and corners, for any cracks in the plastic or dents in the metal.
- Check for Deep Scratches: Minor scuffs are normal, but deep gouges that have gone through the finish cannot be repaired.
- Examine the Mounting Clips: This is critical. Flip the plate over and inspect all the plastic and metal clips. If multiple clips are broken, the plate will not sit securely and may rattle or pop out of place.
- Verify Illumination (If Applicable): If buying an illuminated version, ask the seller to provide a video of it connected to a 12V power source to confirm the LEDs work. A non-functional illuminated plate has no value over a standard one.
- Match the Part Number: To ensure you get the correct version (standard vs. illuminated), match the part number from your old plate or use the numbers in the table above.
Replacement Guide (Difficulty: 1/5)
Replacing the trunk sill plate is a simple DIY job that typically takes less than 30 minutes. The process is the same whether you are replacing a standard plate or upgrading to the illuminated version.
Pro Tip: Use plastic trim removal tools to pry off the old plate. A screwdriver can easily scratch the surrounding plastic trim or the vehicle's paint.
Tools Needed:
- Plastic trim removal tool set
- Socket wrench
- Torque wrench
Step-by-Step Instructions:
- Remove Cargo Tie-Downs: Open the trunk. Use a small flat tool to pop the covers off the cargo tie-down loops located on the trunk floor near the sill. Remove the bolts securing them.
- Remove the Old Sill Plate: Using a plastic trim removal tool, carefully pry upwards along the edge of the sill plate. It is held in by a series of clips. You may need to pull it up and then rotate the bottom edge toward the inside of the trunk to release it fully.
- Connect Wiring (Illuminated Version Only): Locate the connector for the main trunk light, usually on the passenger side of the trunk opening. Disconnect it. The new illuminated sill plate has a 'daisy-chain' or pass-through harness. Plug the sill plate's male connector into the trunk light, and plug the original trunk light connector into the sill plate's female connector.
- Install the New Sill Plate: Align the clips on the new sill plate with the slots in the vehicle body. Press down firmly and evenly until all the clips snap into place. Ensure the weatherstripping sits correctly over the edge of the new plate.
- Reinstall Cargo Tie-Downs: Reinstall the cargo tie-down loops and their bolts. Tighten the bolts to 20 Nm (15 lb-ft). Snap the plastic covers back on.
- Test the Light: If you installed an illuminated plate, close and open the trunk to ensure it lights up correctly.
Known Issues, Recalls, and TSBs
There are no specific recalls or Technical Service Bulletins (TSBs) from GM or the NHTSA that relate directly to the trunk sill plate for the 2016-2020 Cadillac CT6. While the vehicle has several recalls for other issues like seat belts and exterior lighting, none apply to this specific part.
Cost Comparison
| Part Type | Estimated Cost |
|---|---|
| New OEM (Illuminated) | $215 - $275 |
| Used OEM (Illuminated) | $75 - $150 |
| New Aftermarket | Not commonly available |
| Shop Labor | $75 - $150 |
Frequently Asked Questions (FAQ)
Can I upgrade my standard trunk sill plate to the illuminated version?
Yes. The illuminated sill plate (Part No. 84263852) is designed as a plug-and-play upgrade. The wiring harness connects directly to the existing trunk light circuit without any cutting or splicing.
Is it difficult to replace the trunk sill plate myself?
No, this is considered a very easy DIY job with a difficulty of 1 out of 5. It requires basic tools and about 30 minutes. The main challenge is carefully prying off the old plate without breaking any clips on the surrounding trim panels.
Why did my illuminated sill plate stop working?
The most likely causes are a loose connection where it plugs into the trunk light harness, or the internal LED element has failed. First, check the connections. If they are secure, the plate itself likely needs to be replaced.
What does the torque spec for the cargo loops mean?
The 20 Nm (15 lb-ft) torque specification is the required tightness for the bolts that hold the cargo tie-down loops. Using a torque wrench ensures they are tight enough to be secure but not so tight that they damage the threads or the part.
Technical Specifications
OEM Part Numbers: 84263852 23506072 84162549
Material: Plastic or Plastic with Stainless Steel insert. Connection type (illuminated version): Pass-through connector that interfaces with the main trunk light.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- CADILLAC CT6:
- 🛍️ Shop This Part
- Symptoms of a Failing Trunk Sill Plate
- Cosmetic Damage
- Illumination Failure (Upgraded Models)
- Part Variants and Compatibility
- Buying a Used Trunk Sill Plate
- What to Check:
- Replacement Guide (Difficulty: 1/5)
- Tools Needed:
- Step-by-Step Instructions:
- Known Issues, Recalls, and TSBs
- Cost Comparison
- Frequently Asked Questions (FAQ)
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