Component Tests and General Diagnostics

Checking the supply voltage/ground terminal

Checking the power supply and ground terminal

Power supply, steering wheel module (SWM)
The steering wheel module (SWM) is powered via a power input on the control module.
Power input terminal #C1 (#1) receives +30-supply via fuse F3 in the relay/fusebox engine compartment (FJB) from the battery.

Checking the power supply
Check the power supply cable from the battery to steering wheel module (SWM) terminal #C1 (#1). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse. The voltage must be approximately battery voltage.

Ground terminal, steering wheel module (SWM)
The steering wheel module (SWM) has a ground input. The ground input from the control module is power ground and is connected to ground terminal 63/5 in the car body. See the relevant wiring diagram for further information about the ground terminal.

Checking the ground terminal
Check the ground lead between steering wheel module (SWM) terminal #C4 (#4) and the ground terminal. Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. With the ignition on, the drop in voltage between the ground connection for the steering wheel module (SWM) and the ground terminal must not be greater than 0.5 V.
Remedy as necessary.

Other information
- Connecting the breakout box, B5254T7 Connecting the Breakout Box, Steering Wheel Module (SWM)
- Signal description, Steering wheel module (SWM), B5254T7 Signal Description, Steering Wheel Module (SWM)
- See the relevant wiring diagram for information about circuit and ground terminals in the bodywork
- Checking wiring and terminals Checking Wiring and Terminals.





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