Breakdowns attributed to car computer faults, particularly those involving the Body Control Module (BCM), have more than doubled since 2020, positioning them among the leading causes of vehicle failures, according to the AA.
These BCM-related issues now account for approximately 36,000 breakdowns annually, making them the fifth most common reason for the AA to be called out between July 1, 2025, and June 30, 2026. The most frequent reasons for roadside assistance during this period were 12-volt battery problems, followed by issues with tires, the engine or clutch, and the alternator or starter motor.
The BCM functions as the electronic hub for numerous vehicle systems, controlling features such as lights, windows, wipers, alarms, and central locking. A fault in this module can affect multiple systems simultaneously, often with little prior warning. Potential causes for BCM malfunction range from driver error and key chip problems to physical damage, inadequate repair work, or internal computer glitches.
When a BCM fails, it can lead to a variety of malfunctions, from dashboard warning lights to inoperable windows. Security systems are also vulnerable, as the BCM manages the theft alarm, potentially increasing the risk of vehicle theft. Diagnosis typically involves connecting a diagnostic tool to the car's computer system to read error codes. Technicians advise seeking a second opinion if a BCM fault is suspected, as replacement can be costly. Repairing a faulty BCM, if possible, may offer a more economical and faster solution compared to full replacement.