CEM-DF03 - CAN-H, low speed network. Signal too high
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 modelsC30 (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)
- Volvo C30 (2007–2013)2007–2013
- Volvo C30 Electric (2011–2013)2011–2013
- Volvo C70 (2006–2013)2006–2013
- Volvo S40 (2004–2013)2004–2012
- Volvo S60 (2001–2009)2005–2009
- Volvo S80 (1999–2006)2005–2006
- Volvo V50 (2004–2013)2004–2012
- Volvo V70 (2000–2008)2005–2008
- Volvo V70 XC / XC70 (2001–2007)2005–2007
- Volvo XC90 (2003–)2005–2015
What does this fault code mean?
The CEM measures CAN H on the low speed network as too high, which comes from a short to supply voltage in the network. Communication between the control modules is disturbed, so central locking, gauges, instrument lighting and the radio can be affected. The fault most often lies in the wiring, or in a control module sending faulty messages.
Possible causes
- The CAN H wire on the low speed network is shorted to supply voltage
- Short to supply voltage somewhere else on the low speed network
What you can do
- 1Check that the cable harness is not chafed, pinched or damaged by moisture, especially where the CAN wires run close together
- 2Check the connectors on the CAN network for loose connections, corrosion and damage
- 3With a diagnostic tool, read the fault codes from all control modules. Communication faults in several modules point to a shared fault in the network
- 4Use a multimeter to check that the CAN H wire is not shorted to supply voltage. Compare it with the CAN L wire if in doubt
- 5If the fault remains after the wiring has been checked, a control module sending faulty messages may be the cause. A workshop with diagnostic equipment is then needed to find it
- 6The CEM should not be replaced for a CAN fault until a workshop has confirmed an internal fault in the CEM
Symptoms you may notice4
- The central locking does not work at all
- Radio interference
- No gauges work
- The instrument panel lighting does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.