B1299: Power Supply Sensor Circuit Short To Ground

B1299 is set by the body control module (BCM) when it detects that a sensor's power supply circuit has a direct path to ground. The BCM supplies reference voltage -- typically 5V -- to a group of body electronics sensors. When something on that circuit pulls the voltage to ground, the BCM detects the drop and logs B1299. Because multiple sensors can share the same supply rail, this fault can affect several systems at once, making it appear more complex than it actually is.

The most common physical causes are a chafed or pinched wire in the body harness that has worn through to bare metal and contacted a ground point, moisture ingress into a connector causing a conductive bridge, or a sensor with an internal failure that's shorting its supply pin to its ground pin internally. Because of the wiring involved, this fault appears more frequently on higher-mileage vehicles or those that have had body repairs or accessory installations that disturbed the factory harness routing.

Diagnosing B1299 starts with a wiring inspection rather than replacing sensors. Disconnect sensors on the affected supply circuit one at a time while monitoring the reference voltage -- when the voltage recovers after unplugging a specific sensor or connector, you've found the short. A wiring diagram specific to your make and model is essential here since the affected sensors vary significantly. Repair the harness or replace the shorted sensor once isolated.