The chart below summarizes the input and output signals to and from the accessory electronic module (AEM) (4/78). The signal types are divided into directly connected signals and Controller area network (CAN) communication. The following illustration displays the same information with the Volvo component designations.

NOTE:

The signals are only available for installed accessories.

Input signals	Output signals
Directly connected: The reverse warning system control module transmits a buzzer signal (mute signal) Remote start module (mini call, remote control) for remote starting the parking heater (start/stop signal) The tele-mute signal from after market hands free units to the carphone to mute the volume on the audio module (AUM) (AUD) or after market radio unit.	Directly connected: Four signals for RTI (road traffic information) for Japan: Speed Reverse gear indication Lighting signal X-supply to the relay. Parking assistance module (PAM) (voltage and ground terminal) Start for the parking heater consisting of +12V to the relay for the electrical parking heater External alarm unit (trigger signal/power supply) Signal for integrating an after market radio unit (tele-mute signal, speed signal, rheostat signal and controlled power supply to the external antenna amplifier) Tele-mute signal from an after market handsfree unit to an after market radio unit Mini call unit for remote start, supply and ground terminal connection.
Via Controller Area Network (CAN):	Via Controller Area Network (CAN):
Central electronic module (CEM) (4/56): Start and stop signal, to control the relay for the electrical parking heater Reverse gear indication to start the reverse warning system Reverse gear indication, for the RTI (road traffic information) system (Japan) Vehicle speed signal, used by after market radio units and the traffic information system, RTI for Japan Alarm status, used by the accessory electronic module (AEM) controlled external alarm Light position, indicates parking lamps, low and full beam. Used by RTI (road traffic information) for Japan for the background lighting of the navigation display Indication to not start the reverse warning system when a trailer is connected. Activated by switching on the turn signal lamps. Audio module (AUM) (16/1): Indicates the brightness of the background lighting.	Central electronic module (CEM) (4/56): Remote start to activate the parking heater. Audio module (AUM) (16/1): Tele-mute signal Reverse warning signal.

Fig 1: AEM Flow Chart

Courtesy of VOLVO CARS OF NORTH AMERICA.

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

Use the Manual With the Right Hardware

When to See a Mechanic

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