It's How You Play the Game - S4-E19
Continuity mistake: At the scene of the vehicle accident, when Roy's on the Biophone with Rampart the squad's lightbar is on properly, the center chrome piece has vertical slats that face forward. However, after the victim is removed from his vehicle, when Johnny's on the line with Rampart note the squad's lightbar again, the center chrome is now on backwards, the solid side faces forward.