Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
System Overview: Signals
The table below summarizes the input signals to and output signals from the accessory electronic module (AEM) (4/78).
The signal types are divided into directly connected signals and Controller area network (CAN) communication. The illustration below displays the same information with the Volvo component designations.
The signals are only available for installed accessories.
| Input signals | Output signals |
Directly connected:
|
Directly connected:
|
| Via Controller Area Network (CAN) communication: | Via Controller Area Network (CAN) communication: |
Central electronic module (CEM)
(4/56):
Steering wheel module (SWM) (3/254):
|
Infotainment control module (ICM)
(16/1):
Central electronic module (CEM) (4/56):
|
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.