2014-2020 BMW i8 Taillight & Back Up Light Failures and Replacement

Understanding the BMW i8 Back Up Light System

Unlike many cars where a back up light is a simple, replaceable bulb, the 2014-2020 BMW i8 uses a sophisticated, fully integrated LED taillight assembly. The reverse light function is built directly into this sealed unit. This means that if the back up light fails, you cannot simply swap out a bulb; the entire taillight assembly must be replaced. This design is crucial for the i8's unique styling and aerodynamic profile 🎬 See a tutorial on customizing BMW i8 lighting colors but makes repairs more complex and costly.

Symptoms of Failure

A failing back up light on an i8 will present several clear symptoms. Because it's an LED unit, failure might not be as simple as the light just going out.

• "Reversing light failure" message: The most common indicator will be a Check Control warning message 🎬 Watch this video on diagnosing BMW backup light faults on the driver's information display.
• Light is completely out: One or both reverse lights do not illuminate when the car is put into reverse.
• Flickering or dim light: The LED elements may flicker, appear dim, or only partially light up. This often points to a problem with the internal circuitry or LED driver.
• Condensation or water inside the lens: Moisture inside the taillight assembly is a serious issue. It indicates a failed seal and can quickly lead to corrosion and failure of the internal electronics. While minor condensation that disappears quickly might be considered normal for some modern vented lights, persistent moisture or visible water droplets are a sign of a defect.

Known Issues, TSBs, and Recalls

While there are no specific recalls or Technical Service Bulletins (TSBs) for the back up light on the BMW i8, there are several related items to be aware of:

• Condensation: The most frequently discussed issue in owner forums is moisture ingress into the taillight assemblies. This is a common problem across many modern BMW models with large, complex LED lights. A bad seal is the typical cause, and replacement is the only reliable fix.
• Electrical System Recalls: The i8 has had several recalls related to its complex electrical systems, including for the high-voltage battery and Electric Motor Electronics (EME) module. While not directly related to the taillights, these highlight the sensitivity of the vehicle's electronics. A general electrical issue could potentially manifest in lighting problems.

Buying a Used Back Up Light (Taillight Assembly)

Since a new OEM taillight for an i8 is very expensive, a used OEM unit is a practical choice. However, careful inspection is critical to avoid buying a part that is already failing.

Physical Inspection Checklist:

• Check for Cracks and Scratches: Carefully inspect the lens and housing for any cracks, even hairline fractures. A small crack can let in water, leading to failure. Deep scratches can also compromise the integrity of the plastic.
• Look for Signs of Moisture: Examine the inside of the lens for any signs of past or present water intrusion. Look for a faint white residue, water lines, or fogging that won't go away. This is the biggest red flag for a used i8 taillight.
• Inspect All Mounting Tabs: Ensure all plastic mounting tabs and posts are intact and free of cracks. These are essential for a secure, flush fit. Broken tabs are common on parts removed from salvaged vehicles.
• Examine the Wiring and Connector: Check that the electrical connector is clean, with no bent or corroded pins. Ensure the wiring pigtail hasn't been cut or damaged.
• Verify the Part Number: Double-check that the OEM part number on the unit matches the one required for your vehicle's side (left or right). The primary part numbers for the main taillight assemblies are 63217310781 (Left) and 63217310782 (Right).

Why Used OEM is the Best Choice for the i8

For a specialized vehicle like the BMW i8, there are virtually no reputable aftermarket taillight options. A used OEM part provides the exact same fit, finish, and quality as a new part from the dealer. It will connect to the vehicle's wiring and be controlled by the onboard computer systems without any compatibility issues, which is not guaranteed with non-existent aftermarket alternatives.

Cost Comparison

The cost of replacing an i8 taillight varies significantly between new and used options. As it is an integrated LED unit, there are no aftermarket or remanufactured versions available.

Replacement Procedure

Replacing the taillight assembly on a BMW i8 is a straightforward process for a DIYer with basic tools. The difficulty is low compared to other repairs on this vehicle.

1. Access the Assembly: Open the rear tailgate/engine cover. You will need to remove an interior trim panel in the trunk area to access the back of the taillight. This panel is typically held by clips.
2. Disconnect and Unbolt: Disconnect the main electrical harness from the taillight assembly. Then, locate and remove the nuts (usually 3 or 4) that secure the assembly to the car's body.
3. Remove the Old Unit: Carefully push the threaded studs from the inside to pop the taillight out. Be prepared to support its weight as it comes free.
4. Install the New Unit: Position the new assembly, ensuring it sits flush with the bodywork. Hand-tighten the nuts, then snug them down evenly. Do not overtighten, as this can crack the plastic housing.
5. Reconnect and Test: Plug the electrical connector back in. Before reinstalling the trim panel, have a helper confirm that all light functions (tail, brake, turn signal, and reverse) are working correctly.

Frequently Asked Questions