Scania fault code 5121

Code 5121 is used by 3 different Scania systems. Choose the control unit shown in your diagnostic tool:

ZF ZF gearbox No CAN message Error message or no CAN message. Read explanation → MGU Electric machine, calibration failed Checking the rotor position failed when starting the MGS system. Read explanation → GSC Gas regulator, falling pressure Pressure in the high pressure part decreases at start-up, even though the tank valves are closed. The check is run if the low pressure system is unpressurised. Read explanation →