Component Tests and General Diagnostics

Checking the voltage / ground terminal

Checking the power supply and ground terminals

Power supply, trailer module (TRM)
The trailer module (TRM) is powered via a power input on the control module.
Power input terminal #C2 is supplied with +30 from the battery via a fuse. The fuse is located in the integrated relay / fusebox in the engine compartment. It will not be possible to activate the control module if there is an open-circuit.

Checking the power supply
Check the power supply cable from the battery to the trailer module (TRM) terminal #C2. 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, trailer module (TRM)
The trailer module (TRM) has a ground input. The ground input from the control module is power ground and is connected to the ground terminal in the car body. See the relevant wiring diagram for further information about the ground terminals in the bodywork.

Checking the ground terminal
Check the ground lead between trailer module (TRM) terminal #B4 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 control module and the ground terminal must not be greater than 0.5 V.
Remedy as necessary.

Other information:
- Connecting the breakout box Connecting Breakout Box, Trailer Module (TRM)
- Signal specification Signal Specification, Trailer Module (TRM)
- See the relevant wiring diagram for information about circuit and ground terminals in the bodywork
- Checking wiring and terminals Checking Wiring and Terminals

Continue - DONE

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