What does fault code CEM-DF04 mean?

Diagnostic fault code details for CEM-DF04 (Volvo C30 (2007–2013), Volvo C30 Electric (2011–2013), Volvo C70 (2006–2013)). Repair service at OBD Tuning.

VOLVO

CEM-DF04 - CAN-L, low speed network. Signal too low

System

Central Electronic Module (CEM)

Volvo models this fault code applies to

This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.

Applies to the following models:

10 models

C30 (2007–2013), C30 Electric (2011–2013), C70 (2006–2013), S40 (2004–2013), S60 (2001–2009), S80 (1999–2006), V50 (2004–2013), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)

Show models by year and engine (10)

What does this fault code mean?

The CEM detects a short to earth on CAN L in the low speed network, and the signal becomes too low. Communication between the control modules can then break down, and central locking and the radio may be affected. The fault most often lies in the cable or a connector in the network.

Possible causes

Short to earth on the CAN L wire in the low speed network, for example where the insulation has worn through
Contact resistance in the connections in the network

What you can do

1Read the fault codes from every control module you can reach, and note which ones also show communication faults
2Gently flex the cable harness and tug the connectors with the ignition on. If the communication faults change, that shows where in the network the fault is
3Use a multimeter to check that the CAN L wire has no contact with earth or the body along its length
4Check the connectors on the CAN network for loose connections, corrosion and moisture
5Check that the harness is not chafed or worn against the body, especially at grommets and sharp edges
6The CEM should not be replaced for a CAN fault unless a workshop has confirmed an internal fault in the CEM

Symptoms you may notice2

The central locking does not work at all
Radio interference

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

VOLVO

CEM-DF04 - CAN-L, low speed network. Signal too low

System

Central Electronic Module (CEM)

Volvo models this fault code applies to

This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.

Applies to the following models:

10 models

Show models by year and engine (10)

What does this fault code mean?

Possible causes

Short to earth on the CAN L wire in the low speed network, for example where the insulation has worn through
Contact resistance in the connections in the network

What you can do

1Read the fault codes from every control module you can reach, and note which ones also show communication faults
2Gently flex the cable harness and tug the connectors with the ignition on. If the communication faults change, that shows where in the network the fault is
3Use a multimeter to check that the CAN L wire has no contact with earth or the body along its length
4Check the connectors on the CAN network for loose connections, corrosion and moisture
5Check that the harness is not chafed or worn against the body, especially at grommets and sharp edges
6The CEM should not be replaced for a CAN fault unless a workshop has confirmed an internal fault in the CEM

Symptoms you may notice2

The central locking does not work at all
Radio interference

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

CEM-DF04 - CAN-L, low speed network. Signal too low

Volvo models this fault code applies to

CAN-L, low speed network. Signal too low

CAN-L, low-speed network. Signal too low. Intermittent fault

Applies to the following models:

What does this fault code mean?

Possible causes

What you can do

Symptoms you may notice2

CEM-DF04 - CAN-L, low speed network. Signal too low

Volvo models this fault code applies to

CAN-L, low speed network. Signal too low

CAN-L, low-speed network. Signal too low. Intermittent fault

Applies to the following models:

What does this fault code mean?

Possible causes

What you can do

Symptoms you may notice2