What does fault code CEM-1A5B mean?

Diagnostic fault code details for CEM-1A5B (Volvo S60 (2001–2009), Volvo S80 (1999–2006), Volvo V70 (2000–2008)). Repair service at OBD Tuning.

VOLVO

CEM-1A5B - Communication with the steering wheel module (SWM). Signal missing

System

Central Electronic Module (CEM)

Volvo models this fault code applies to

Applies to the following models:

5 models

S60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)

Show models by year and engine (5)

What does this fault code mean?

The central electronic module (CEM) has lost communication with the steering wheel module (SWM) and sets this code. The fault lies in the communication, not in the CEM, so the CEM should not be replaced. The steering wheel module handles the buttons on the wheel and the cruise control, so several functions operated from the wheel can stop working.

Possible causes

The steering wheel module is not getting power
The ground wire to the steering wheel module is broken
Contact resistance in the connections
Broken CAN wiring to the steering wheel module
Wrong steering wheel module for this car, for example a used module with different software or hardware
A common CAN network fault if several communication faults are stored at the same time

What you can do

1With the ignition on, activate the hazard warning switch. If the hazard lamps start, the CEM has power and ground
2Test the horn. If it sounds, the steering wheel module is probably powered. If the hazard lamps work but the horn does not, check the horn relay fuse in the engine bay.
3Check the steering wheel module fuse. If it has blown, replace it once. If it blows again, use a multimeter to check the wire after it has no contact with ground.
4Check that the connector to the steering wheel module is seated and not corroded or damaged. Use a multimeter to check the ground wire has no break
5After the work, clear the code and check the horn and the wheel buttons. If the code returns, read the module ID with a diagnostic tool if you have one

Symptoms you may notice4

Cruise control does not work at all
The wipers only run at the lowest speed
The turn signals do not work
The buttons on the steering wheel do not work

General guidance for car owners. Diagnosis on the car can point to a different cause.