Manufacturer-specific body code — definition not reliably documented; its meaning varies by make, model, and year, so confirm it against your manufacturer's service information

B1000 is a generic ECU malfunction code on Ford vehicles. The most common cause is a weak battery or corroded battery terminals that cause voltage drops to the body control module. Clean battery terminals, load-test the battery (should hold 12.4V+), and check the BCM ground connections. If the battery and grounds are good, the BCM behind the kick panel may have internal failure.

GM B1000 codes point to a general body control module fault. Check for water intrusion at the BCM location (behind the glove box on most models). A leaking A/C evaporator drain or windshield seal often drips water directly onto the BCM. Dry the module and connectors, then clear codes. If it returns, the BCM needs replacement and programming with a GM Tech2 or equivalent.

On Ford sedans, B1000 is frequently caused by a failing GEM (Generic Electronic Module) or water intrusion through the cowl area. Check the cabin air filter housing for leaf buildup blocking the drain, which causes water to overflow into the electronics. The GEM module on Focus is under the dash on the driver side. Dry everything and clear codes before replacing any modules.