Blue Bird buses equipped with Cummins diesel engines contain an engine control module, or ECM, that continuously monitors the vehicle for problems. When the ECM detects a problem with one or more of the bus's systems, it stores a diagnostic trouble code, or DTC, in its internal memory. These DTCs are alphanumeric codes that correspond to a specific problem within the vehicle. An automotive scan tool connected to the bus's diagnostic data port can retrieve the codes from the ECM's memory.
Turn off the engine and apply the parking brake. Turn the ignition back to the "ON" position, but don't crank or restart the engine.
Plug an automotive scan tool's data cable into the bus's data port, located underneath the dashboard near the steering column.
Press the power button on the scan tool and allow it to boot up. Select "ECM" from the scan tool's main menu.
Select "Read all stored DTCs" from the ECM menu. Write down the DTCs shown on the scan tool's screen.
