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B2100 is a diagnostic trouble code (DTC) for "Driver's Door Key Cylinder Switch Failure". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $79.99. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
The B2100 trouble code detects a failure from the door driver key cylinder switch.
The B2100 code is a generic OBD-II body trouble code that notes a driver's door key cylinder switch failure. The key cylinder switch is directly attached to the driver door lock, and is used to manually lock or unlock the driver door with the key. When the key is inserted into the exterior door lock and rotated, the cylinder switch is activated, and the door will be locked or unlocked. If the key cylinder switch is unable to do its job, the body control module will likely store the B2100 trouble code.
The B2100 trouble code is almost always caused by a defective driver door key cylinder switch. There are a few different components within the cylinder that can fail, but all of them will require the cylinder to be replaced. In very rare cases, the code can be inaccurately detected by a failing body control module.
When the B2100 trouble code is detected, the driver door key lock and unlock system will likely be inoperable. This means that the driver door cannot be locked or unlocked from outside the vehicle using the manual key. In some vehicles, this trouble code will also be accompanied by an illuminated Check Engine Light on the instrument panel.
The B2100 trouble code should be addressed using a standard OBD-II trouble code scanner. While it may seem like the cylinder switch can simply be replaced, the scanner will allow the mechanic to note if there is any potential controller failure, and also check to see if any other trouble codes are present. If there are numerous codes detected, then they will need to be addressed in the order that they appear in. The trouble codes should then be reset, and the vehicle restarted, to see if the code remains detected. If the code is no longer present, and the driver door exterior lock is functioning properly, then the B2100 code was likely detected inaccurately, or is the result of an intermittent error.
If the code remains detected, then the driver door key cylinder switch should be condemned and replaced. The system should then be manually checked, and the trouble codes should be reset, the vehicle restarted, and the code checked for again. If the code continues to be present, then body control module failure should be assumed.
The most commonly made error when diagnosing the B2100 trouble code comes from a failure to abide by the OBD-II trouble code diagnosis protocol. It’s important that mechanics follow the protocol at all times, to ensure a wholly efficient and thorough diagnosis.
It is fairly common for the driver door key cylinder switch to be replaced without ever checking the trouble codes with an OBD-II trouble code scanner. Failure to utilize the scanner during inspections can result in other vehicle problems being overlooked.
The B2100 trouble code will not keep a car from being drivable, or cause any drivability issues. However, the driver door may not be able to be locked or unlocked from the outside, using the manual key. As with all trouble codes, an inspection should be scheduled when the B2100 code is detected.
The B2100 trouble code will almost always be resolved by replacing the driver door key cylinder switch or the body control module.
The B2100 trouble code is a manufacturer specific code, which means that the definition will change depending on the manufacturer. This code detects a driver door key cylinder switch failure in some automakers, but signals a different vehicle body issue for many other manufacturers.
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