BMU5 Inconsistent long term RAM data
• No action is needed if DTC is set a few times (1-5). • If set frequently do the following: • Connect a CAN brake out box to the GMS sub-bus • Have the vehicle running in idle. • Measure differential and common mode disturbances on the GMS sub-bus. • If no disturbances, replace ECU • If high disturbances, check the grounding connection network for the VCB-components. Check all the connections in G63 and all ground points on the other end of each ground cable connected to G63. See drawing 2098187. •If noise remains the filter components in the MGU, VCB central electric unit or DCC might be damaged, Measure the capacitance from + to GND and – to GND. It should be 1,4µF in the MGU, 0,68µF in the central electric unit and 28nF in the DCC. Disconnect the components from the VCB central electric unit before measurement. •Change the faulty component NOTE! Performing measurements within the VCB central electric unit is considered an electrical work and shall only be performed by Scania certified personnel. Vehicle shall be made safe according to electrical work procedure.
What you'll see
No driver-visible symptom recorded.
System reaction
A software reset is performed. Thereafter the system should work normally.
Diagnostic depth
A portion of the internal RAM is used to store configuration data. At system start, compressed information is read from a non-volatile memory. The compressed information is expanded and stored in the portion of RAM used for configuration data. After this initial store, the configuration data should be available for reading only. No change of the information is permitted. The consistency of the data is controlled with a checksum. If the checksum test fails, this DTC is set.
Exposure to extensive electro-magnetic radiations Software flaws.