Component Tests and General Diagnostics

Checking the supply voltage/ground terminal

Voltage feed Accessory USB Unit (AUU)
Accessory USB Unit (AUU) is supplied with voltage via a voltage input on the control module. When the ignition is on, the power input is powered and the control module is in active mode.
1. Power input #A C1:1 is supplied with voltage via a fuse from the battery. This power input is used to power the memory in the control module. In the event of an open-circuit, the control module will be reset and adaptation values and diagnostic trouble codes (DTCs) will disappear.

Checking the power supply
Check the voltage feed cable from the battery to the Accessory USB Unit (AUU) #C1-1 for open circuit, loose connections, contact resistance, and oxidation. Check the fuse. The voltage must be approximately battery voltage.

Ground connection Accessory USB Unit (AUU)
Accessory USB Unit (AUU) has a ground input. See the relevant wiring diagram for further information about the ground terminal.

Checking the ground terminal
Check the ground cable. Check for loose connections, contact resistance and oxidation. Check for an open-circuit. With the ignition on, the drop in voltage between the ground connection for the control module and the ground terminal must not be greater than 0.5 V.
Remedy as necessary.

Other information
- Signal specification Signal Specification, Accessory USB Unit (AUU)
- See the relevant wiring diagram for information about circuits and ground terminals in the bodywork.
- Checking wiring and terminals Checking Wiring and Terminals

Continue - DONE

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