B2108 code definition

The B2108 trouble code detects a trunk key cylinder switch failure.

What the B2108 code means

The B2108 code is a generic OBD-II body trouble code that notes a trunk key cylinder switch failure. The key cylinder switch is located in the trunk door, and allows the trunk to be manually locked or unlocked using the key. When the key is inserted into the trunk lock (located directly next to the trunk handle), and rotated, then the cylinder switch causes the trunk to lock or unlock. If at any point the trunk key cylinder switch is failing to lock or unlock the vehicle, then the body control module will most likely store the B2108 trouble code.

What causes the B2108 code?

The only common cause of the B2108 trouble code is a defective trunk key cylinder switch. There are a few different components in the cylinder switch that may fail, but regardless of what part is defective, the entire cylinder switch will need to be replaced. In very rare cases, the code may be the result of a malfunctioning body control module.

What are the symptoms of the B2108 code?

If the B2108 trouble code is detected, then the trunk likely will not be able to be manually locked or unlocked using the key. It is also possible that the check engine soon Warning Light will illuminate on the gauge cluster.

How does a mechanic diagnose the B2108 code?

An inspection of this code should begin by using a standard OBD-II trouble code scanner. It might seem unnecessary to use a scanner for this issue, which can be easily verified, but a scanner allows the mechanic to assess the body control module, and also to see if there are any additional trouble codes detected. If numerous trouble codes are present, then the mechanic will diagnose them in the order that they appear in. The codes will then be reset, the vehicle restarted, and the B2108 code checked for. If the code has gone away, and the exterior trunk manual lock is functioning properly, then the code was most likely detected erroneously, or is the result of an intermittent error.

If the code remains detected, then the trunk key cylinder switch should be replaced. Once the cylinder switch has been replaced, the trouble codes should again be reset, the vehicle again restarted, and the B2108 code checked for again. If the code remains present, then the body control module has most likely failed.

Common mistakes when diagnosing the B2108 code

The most commonly made error when diagnosing this code comes from a failure to properly abide by the OBD-II trouble code diagnosis protocol. The protocol should always be observed step by step, as this helps ensure thorough and accurate diagnoses.

It is fairly common for the trunk key cylinder switch to be replaced without an OBD-II trouble code scanner being used to check the codes. If this mistake is made, other problems that are present in the vehicle will not be noticed.

How serious is the B2108 code?

The B2108 code will not keep a car from being drivable, or cause drivability concerns. However, the trunk will likely not be able to be manually locked or unlocked with the key, which may cause security or practicality problems. While the B2108 code is not urgent, an inspection should be scheduled when the code is detected.

What repairs can fix the B2108 code?

The B2108 code will almost always be resolved by replacing the trunk key cylinder switch. In very rare cases, the body control module might require replacement.

Additional comments for consideration regarding the B2108 code

The B2108 code is a manufacturer specific code, which means that the definition can vary from automaker to automaker. While this code detects a trunk key cylinder switch failure in some vehicles, it may signal a much different body failure in other cars. The mechanic should always pay attention to the vehicle that is being worked on when diagnosing the B2108 code.

Need help with a B2108 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

This article originally appeared on YourMechanic.com as B2108 OBD-II Trouble Code: Trunk Key Cylinder Switch Failure and was authored by Brady Klopfer.


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