B1299 is a body (B-series) diagnostic trouble code indicating that the body control or related module has detected a short to ground in the power supply circuit feeding a sensor. In normal operation the module supplies a regulated reference or supply voltage to one or more sensors and monitors that line; when the measured voltage drops well below the expected value, the module interprets it as the supply conductor being shorted to ground (chassis or battery negative) and sets this code. Because B-codes are manufacturer-specific, the exact sensor and circuit involved depend on the make and the affected system, but the fault is electrical: the supply rail is being pulled low rather than the sensor itself reading out of range. For the driver, the immediate effect can range from no noticeable symptom to loss of a feature controlled by the affected sensor, a warning lamp, or erratic behavior of the related system. Until the short is repaired the module may disable or default the affected function for safety, and the code will typically remain active or recur because the low-voltage condition is continuously present.

• Warning light or message related to the affected system
• Loss or intermittent operation of the sensor-controlled function
• Erratic or default readings from the affected sensor
• Code remains active or returns immediately after clearing
• Possible related electrical faults stored at the same time
• Blown fuse on the affected supply circuit