Possible fault patterns during the load test

No voltage or no current during the USB test

The USB module cannot be initialized in the IMIB if the USB cable was not connected or there is no voltage supply from the USB port in the vehicle. When this is the case, a message will appear on the IMIB display.

Troubleshooting:

Check USB cable connection between IMIB and vehicle.
Check lines and plug connections in vehicle.
Check the USB connection.
Check control unit.
Check fuse F26.

Line resistance too high during USB test

Fig 1: Line Resistance Versus High USB Test Graph

Courtesy of BMW OF NORTH AMERICA, INC.

The curve progression on the green line (1) drops off significantly in the graphic that is displayed. (Voltage less than 3.9 V at 500 mA)

NOTE: With several USB devices, a voltage of around 4 V is not sufficient to guarantee the function. However, the vehicle is trouble-free! In this case, use a different USB device.

Troubleshooting:

Check USB cable connection between IMIB and vehicle (use spare cable from another IMIB if necessary).
Check the USB connection.
Check lines and plug connections in vehicle.

Overloading during the USB test

Fig 2: Overloading During USB Test Graph

Courtesy of BMW OF NORTH AMERICA, INC.

The vehicle is not able to deliver the required level of current. The voltage (1) collapses and the current is thus limited.

Troubleshooting:

The customer may have attached a USB hub (distributor) to the vehicle USB connection. Always run the USB test directly on the USB connection in the vehicle!
Check the USB connection.
Check lines and plug connections in vehicle.
Check control unit.

NOTE: If the test was not successful, a vehicle diagnosis must be carried out with ISTA!