This wiring diagram manual provides detailed electrical schematics for Volvo B9TL buses equipped with D9B engines, covering chassis numbers from 123057 to 132838. It includes comprehensive layouts of electrical systems, circuit connections, and component locations. The manual is essential for diagnosing and repairing electrical issues, offering precise guidance for troubleshooting and maintenance. This document is crucial for technicians and electricians to ensure the proper functioning and safety of the electrical systems in these bus models.