For all work on the extraction line of the fuel supply system of the Clean Energy Control Unit in BMW Hydrogen 7 vehicles, this extraction line must be relieved of pressure in advance. The delivery line, i.e. the hydrogen ”rail”, is emptied by the engine operated in the hydrogen mode.
This initial measure can be carried out using the present service function. The vehicle must be at a standstill and the bivalent engine must be running in the hydrogen mode.
If the vehicle is not at a standstill, the service function is aborted!
Operating principle and sequence of the service function:
During the hydrogen mode, the filling valve for gaseous refuelling as well as the engine shutdown valve and also the pressure regulator are open. After requesting the service function to relieve the delivery line, the filling valve is closed. The engine continues to run in the hydrogen mode until the pressure in the hydrogen ”rail” is no longer sufficient. The engine management system then runs an automatic changeover to the petrol mode. This closes the pressure regulator.
If no changeover to the petrol mode takes place within 30 seconds, the function is aborted!
Directly after (approx. 100 milliseconds) the changeover to the petrol mode, a brief query is run to determine whether the pressure at the pressure sensor for the partial-flow control valve as well as at the pressure sensor for the engine shutdown valve and in the hydrogen ”rail” is between 0 and 2 bar overpressure.
In the event of a fault, the function is aborted here!
Fault 0x64C0 can be stored in the Clean Energy Control Unit!