The table below summarizes the input signals to and output signals from the trailer module (TRM). The signal types are divided into directly connected signals and CAN communication. Fig 1 displays the same information with the Volvo component designations.

Input signals	Output signals
Directly connected:	Directly connected:
Stop lamp signal from Central electronic module (CEM) (4/56) via left tail lamp.	To tow hitch cable harness: Right turn signal lamp Left turn signal lamp Stop lamp right Stop lamp left Parking lamps Back-up lamp Fog lamps Charging (+12 V voltage).
Via Controller Area Network (CAN) communication:	Via Controller Area Network (CAN) communication:
Central electronic module (CEM) (4/56)	Central electronic module (CEM) (4/56) Driver information module (DIM) (5/1) Differential electronic module (DEM) (4/82) (option) Parking Assistance Module (PAM) (4/86) (option) Parking Assistance Camera (PAC) (4/120) (option)

Fig 1: Identifying Input Signals And Output Signals From Trailer Module (TRM)

Courtesy of VOLVO CARS CORPORATION

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

System Overview: Signals

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When to See a Mechanic

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