Volvo VNL 780 Operator's Manual page 458

448 MAINTENANCE AND LUBRICATION
The vehicle is equipped with systems that have their own electronics, including vehicle ECU
(VECU), ABS, air bag (SRS), gauge cluster and some transmissions. Disconnect each
ECU at its electrical connectors.
Disconnect the power harness (engine electronic control unit [EECU]) and vehicle interface
harness at the battery.
Disconnect the electrical connections at the negative side of the battery.
W8003198
W8003199