Component Tests and General Diagnostics

Checking the power supply and ground terminal

Power supply, trailer module (TRM)
Trailer module (TRM) is supplied with voltage via a voltage input on the control module.
The power input is powered with the ignition off and on. The Trailer module (TRM) is in active mode with the ignition on.
- The power input is powered via two fuses from the battery. The Trailer module (TRM) will not be activated if there is an open-circuit.

Checking the power supply
Check the power supply cable from the battery to Trailer module (TRM) terminal #C1:2(#32). Check for an open-circuit. Check for loose connections, contact resistance and oxidation. Also check the fuses. The voltage must be approximately battery voltage.

Ground terminal, trailer module (TRM)
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 terminal.
- Ground input #C2:4(#25) is power ground and is connected to the ground connection in the body.

Checking the ground terminal
Check the ground cable between the Trailer module (TRM) terminal #C2:4 (#25) and the ground terminal. Check for an open-circuit. Check for loose connections. Check for contact resistance and 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.
For the trailer lights to work correctly, it is important to also check the ground connection in the socket for the trailer connector. Check the ground cable between the socket for the trailer connector and ground connection in the vehicle for open circuit, loose connection, contact resistance and oxidation.
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 circuits and ground terminals in the bodywork.
- Checking wiring and terminals Checking Wiring and Terminals

Continue - DONE

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