2020-2025 Corvette & Cadillac CT5 Headlight Control Module: Failures, Recalls, and Programming Explained

Function of the Headlight Control Module

The Headlight Control Module (HCM) is a critical electronic unit in the 2020-2025 Chevrolet Corvette and 2020-2024 Cadillac CT5. These vehicles are built on General Motors' sophisticated "Global B" electrical platform, which relies on a network of smart modules to control vehicle functions. The HCM specifically governs the full LED headlight assemblies. It takes commands from the driver (via the headlight switch) and data from environmental sensors (like the ambient light sensor that detects darkness) to operate the headlights correctly. It manages power for the low beams, high beams, and Daytime Running Lights (DRLs), and on some trims, it may control adaptive lighting features. When it fails, your headlights can become unreliable or stop working altogether, posing a significant safety risk.

Common Symptoms of a Failing Headlight Control Module

When the headlight module begins to fail, you may notice one or more of the following symptoms. Since the entire headlight assembly is a sealed LED unit on these models, a bulb cannot be replaced; the issue often lies with the control module or internal drivers.

• One or Both Headlights Won't Turn On: The most obvious sign is a complete failure of one or both headlights, even though the LED elements are not burned out.
• Intermittent Flickering or Dimming: The headlights may flicker, dim, or shut off randomly while driving. This can sometimes be triggered by bumps or turns.
• Beams Stuck in One Mode: You may be unable to switch between high and low beams, or the lights may be stuck on high beams, potentially glaring other drivers.
• Automatic Headlights Malfunction: In "Auto" mode, the headlights may not turn on when it gets dark, or they may stay on during bright daylight.
• Dashboard Warning Lights: A failure in the module can trigger a general lighting system warning light or a specific error message on the driver information center.
• Associated OBD-II Trouble Codes: While a generic scanner may not read them, a professional scan tool may find Body (B-prefix) or Network (U-prefix) codes. Specific codes like P0606 (Control Module Internal Performance) or B108E (Ambient Light Sensor Signal) have been linked to lighting module software issues in GM vehicles.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

Both the Corvette and CT5 have been subject to several recalls related to lighting control software, which is often managed by the Body Control Module (BCM) in conjunction with the headlight modules. In most cases, the fix is a software update, not a hardware replacement.

Recall N232431050 (Canadian Regulation Issue)

This recall affects a wide range of GM vehicles, including the 2020-2024 Corvette and 2020-2024 Cadillac CT5. The issue is that the low-beam headlights may fail to turn on automatically in the dark when the switch is left in the "Off" or "Parking Lamp" position. This violates Canadian motor vehicle safety standards. The fix is a software update for the Body Control Module (BCM) performed by a GM dealer.

Recall N222386380 (U.S. Non-Compliance)

Affecting 2020-2023 Cadillac CT4 and CT5 models, this recall was issued because the Daytime Running Lights (DRLs) may not deactivate when the main headlights are turned on. This can create excessive glare for oncoming drivers, increasing the risk of a crash. The remedy is a BCM software update. A remedy for 2020 models was delayed but should now be available.

Corvette Stop-Sale (Recall N252541250)

This issue prompted a stop-sale for thousands of 2025 and some 2026 model year Corvettes. A software bug in the exterior lighting control module prevents the car from notifying the driver if a rear turn signal fails. This violates federal safety standards which require an indication of bulb failure (like a hyper-flashing indicator). The fix is a software update, which can be done over-the-air (OTA) for 2026 models but requires a dealer visit for affected 2025 models.

Programming and Calibration: What You MUST Know After Installation

A replacement Headlight Control Module MUST be programmed to the vehicle. The Corvette C8 and Cadillac CT5 use GM's Global B electrical architecture, which features advanced cybersecurity. You cannot simply swap a used or new module and expect it to work.

• Dealer Programming: A GM dealer uses a subscription-based software platform called Techline Connect to program and register a new module to your vehicle's VIN.
• Independent Shop Programming: An independent repair shop can perform the programming, but only if they have invested in a compatible J2534 pass-through device and maintain an active, paid subscription to GM's Service Programming System (SPS).
• Pre-Programmed Modules: Some specialized third-party companies sell brand-new OEM modules that are pre-programmed to your vehicle's VIN before they are shipped. This allows for a true plug-and-play installation at home without requiring a trip to the dealer, which can be a convenient and cost-effective option.

Buying a Used Headlight Control Module

Purchasing a used Headlight Control Module can be a cost-effective way to source the part, but it comes with important considerations. While the hardware itself is often reliable, the main challenge is programming.

• Verify the Part Number: Match the part number exactly. Known OEM part numbers include 13542926 and 13547243, but supersessions may exist. When in doubt, confirm with a dealer using your VIN.
• Physical Inspection: Check for any signs of physical damage, especially corrosion on the connector pins or cracks in the housing. On the C8 Corvette, the module is mounted on the top of the headlight assembly, which helps protect it from moisture.
• Factor in Programming Costs: A used module from a salvage yard might cost under $50, but you must add the cost of dealer or independent shop programming, which can be $150-$250 or more.
• Consider Pre-Programmed New OEM: For these specific vehicles, buying a new OEM module that is pre-programmed to your VIN from a specialist may be a better value. It eliminates the need for a separate programming appointment and ensures the module has the latest software and is configured correctly for your car's options right out of the box.

Replacement Cost Comparison

The cost to replace a Headlight Control Module can vary significantly based on the part source and labor.

Frequently Asked Questions (FAQ)