Home › Land Rover › 2013 › Range Rover Sport Supercharged › Repair and Diagnosis › Restraints › Restraints Control Systems › Diagnostic Trouble Code Index DTC: Restraints Control Module (RCM) -- Range Rover Sport/L320 › Diagnostic Trouble Code Index DTC: Restraints Control Module (RCM) › Description And Operation › DTC B0021-1A: Left Curtain Deployment Control 1 - Circuit resistance below threshold › Possible Causes