Here share the real repair case on BMW BMW F10 525i CID Prompt:Battery Discharge Warning.
Model: BMW F10 525i
Mileage: 45,000 miles
“The CID prompt:battery discharge when starting the engine at first time on every morning”the customer said.
After driving testing,found that coolant pumps kept running at hight speed for a long time after engine off and locking car.And technicians found the pump was stopped forcibly by power management system at condition of voltage reduction.
And after reading the DTCs,but there was not any trouble codes releated to pump.Check the circuit diagram 1,the pump is controled by ECU.Observe the controled signal waveform(figure 2),but did not find any abnormalities.
Checked the temperature of cooling liquid,ECU cabin and engine oil,there was not exception exist.And if these temperature data are abnormal,then the cooling fan will rotate at hight speed,but it didn’t.
Finally,technicians determined the trouble was occured on the electronic pump.It was found that the pump was still running at high speed without ECU controled signal after locking car.It indicated that there were something wrong on the internal controller.
Replaced the electrical pump,the trouble sloved.