Service Bulletin

Bulletin No.: 01-08-42-001Q
Date: January, 2025

INFORMATION
Subject:

Exterior Lamp Condensation and Water Leak Information and Replacement
Guidelines

Models:

2025 and Prior GM Passenger Cars and Trucks (including Medium Duty
Trucks)
(Excluding LCF Medium Duty Trucks)

Attention:

Involved Region or Country: North America, Europe, Uzbekistan, Russia,
Middle East, Iraq, Israel, Palestine, Argentina, Brazil, Bolivia, Chile,
Colombia, Ecuador, Paraguay, Peru, Uruguay, Venezuela, Japan, Cadillac
Korea (South Korea), GM Korea Company, China, Taiwan, Thailand,
Singapore, Philippines, Australia/New Zealand, Egypt, Other Africa, South
Africa

This bulletin has been revised to add the 2025 Model Year. Please discard Corporate
Bulletin Number 01-08-42-001P.
Dealers in the U.S. and Canada Only: Please follow Service Bulletin # 18-NA-306 and the pre-authorization
process prior to warranty replacement of front headlamps in 2021 and newer model year vehicles.

The following information is being provided to better define the causes of condensation in exterior lamps and
includes guidelines for determining the difference between a lamp with a normal atmospheric condition (condensation) and a lamp with a water leak. If the lamp is determined to have condensation and not a leak, this should be
explained to the customer and their lamp should not be replaced in warranty.
Some exterior lamps, such as cornering, turn signal, backup, headlamps, side marker, fog lamps, or tail lamps may
exhibit a fine mist or white fog (condensation) on the inside of the lamp lens. This may be normal during certain
weather conditions or following a carwash.
Condensation occurs when the lens surface, through atmospheric changes, reaches the “dew point.” When this
takes place, the moisture in the air within the lamp assembly condenses, creating a fine mist or white fog on the
inside surface of the lamp lens.
Most exterior lamps on General Motors vehicles use a vented design. They are designed to remove any accumulated moisture vapor by expelling it through a vent system. The vent system always operates; however, it is most
effective when the lamps are ON and when the vehicle is in motion. Depending on the size, shape, and location of
the lamp on the vehicle, and the atmospheric conditions occurring, the amount of time required to clear the lamp
may vary from 2 to 6 hours. Customers with short commutes will experience a longer time to clear the lamp. If a
customer states that the moisture in their lamp “comes and goes”, this is likely condensation and not a leak and the
lamp should not be replaced.

Copyright 2025 General Motors. All Rights Reserved.

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Bulletin No.: 01-08-42-001Q

Condensation Examples (Do Not Replace Lamp Assembly Under Warranty)

3789054

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A Fine Mist or White Fog on the Inside Surface of the Lamp Lens Occurring After a Period of High Humidity
Important: Moisture is most noticeable during the Spring and Fall of each year, due to high humidity and the large
fluctuation in temperature between day and night.
Note: Any of the conditions listed below would indicate NOT to service / replace the lens or lamp assembly.
• May be located primarily in the lens corners or edges
• The condition should clear of moisture when the vehicle is parked in a dry environment, or when the vehicle is
driven with the lights ON. Place the vehicle in a dry environment and turn on the lights for 60 minutes. Do not
replace the lamp if the condition has significantly improved after 60 minutes.
• A comparison of the equivalent lamp on the opposing side of the vehicle indicates a SIMILAR performance.
(Condensation can occur in one or both lamps. Leaks are more likely to occur on one side at a time.)
Note: A different performance of lamps on opposite sides of a vehicle DOES NOT always indicate that one lamp is
bad, and the other is normal. For example, on a cold day when the sun is hitting only one side of the vehicle, the
normal condition of one side showing clear and the other showing fogging/moisture, could be misinterpreted as a
bad lamp. The customer may comment that, or you may need to inquire if, the moisture “comes and goes.” Moisture
“coming and going” is considered a normal condition.
If the above conditions are noted, the customer should be advised that replacement of a lamp assembly may not
correct this condition as it is likely a function of weather / other conditions outside the vehicle. The lamp assembly
should not be replaced under warranty for this reason.

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Water Leak Examples

3803382

3789062

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Numerous & Various Size Drops of Water Collecting on the Inside Surface of the Lamp Lens
Note: Any of the conditions listed below would indicate the need to service the lens or lamp assembly.
• An accumulation of water in the bottom of the lamp assembly.
• A condition that WON'T clear when the vehicle is parked in a dry environment, or when the vehicle is driven with
the lights ON.
• A comparison of the equivalent lamp on the opposing side of the vehicle indicates a different performance.
Note: A different performance of lamps on opposite sides of a vehicle DOES NOT always indicate that one lamp is
bad, and the other is normal. For example, on a cold day when the sun is hitting only one side of the vehicle, the
normal condition of one side showing clear and the other showing fogging/moisture, could be misinterpreted as a
bad lamp. The customer may comment that, or you may need to inquire if, the moisture “comes and goes.” Moisture
“coming and going” is considered a normal condition.

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Internal Coating Issues Examples

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Permanent Staining on the Inside Surface of the Lamp Lens
• Some General Motors lamps have a coating on the inside of the lens to reduce condensation. Occasionally,
there will be an issue where this coating is no longer clear, but instead is always visible.
Important: This failure mode is internal to the lamp lens, if you can feel an issue when running your finger
along the outer lens of the headlamp, it is not an issue with the internal coating streaking.
Note: Any of the conditions listed below would indicate the need to service the lens or lamp assembly.
• The customer reports they have a PERMANENT stain on the INSIDE of the lens. The stain never goes away,
even when the condensation / water inside the lamp is cleared.
If a lamp is found to be exhibiting a leak, review the most recent version of Service Bulletin 02-08-42-001 for
information regarding impact damage and modification inspection.
Non-GM Headlamp, Tail Lamp and Fog Lamp Assemblies
Many companies outside of General Motors are manufacturing lamp assemblies that look very similar to original
equipment. They target high volume programs. These lamps are most often presented by customers as holding
moisture or for inoperative functions due to corroded electrical connections. It appears these non OE lamps get
installed on vehicles as part of a collision repair. Most likely the customer has no idea they are not original
equipment, as the initial appearance is generally good. Obviously, these parts are not covered by warranty. Some of
the common company names seen on these lamps are Eagle Eyes, Srumto, and Depo.

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This fog lamp was returned for retaining moisture. As you can see it is marked with the Depo brand (it is also called
out on the front lens).
The most reliable way to identify a non OE part is to compare it to the replacement service part or a like vehicle.
Many do have the application called out on the part with the letters GM being present but would not typically use a
GM trademark. They often use substandard wiring, sockets, vent patches and unsealed connectors.
Example of GM Trademark
Note: The graphics below are examples of GM Trademarks that appear on GM lamp assemblies. Current assemblies contain a GM trademark in multiple locations including on a label affixed to the assembly and in the approval
marking.

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GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

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