CEM-1A5F - Communication with the brake control module (BCM). Signal missing
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:
5 modelsS60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)
What does this fault code mean?
The central electronic module (CEM) has lost the link to the brake control module (BCM) and sets this code. The BCM controls, among other things, the ABS function, so the ABS warning lamp may light and ABS may be lost. The fault lies in the communication, not in the CEM, so the CEM should not be replaced.
Possible causes
- The BCM is not getting power
- The ground wire to the BCM is broken
- Contact resistance in the connections
- Broken CAN wiring to the BCM
- Wrong BCM 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
- 1Switch the ignition on and check that the ABS warning lamp goes out after a moment. If it stays lit, the fault is still present
- 2Check the BCM fuses. If one has blown, replace it once. If it blows again, use a multimeter to check the wire after it has no contact with ground.
- 3Check that the connectors to the BCM are seated and free of corrosion, chafing or damage. Check that the ground wire is tight and clean
- 4Use a multimeter to check that the wires to the BCM have no break. If the fault remains, read the module ID with a diagnostic tool if you have one
- 5Safety: the brake control module affects the brakes, so have a workshop fix the fault promptly and do not work on the brake system yourself.
Symptoms you may notice3
- The ABS warning lamp is lit
- ABS function is lost
- A message appears in the display
What the fault can affect1
- No ABS function
General guidance for car owners. Diagnosis on the car can point to a different cause.
Common Combinations
CEM-1A5F, CEM-A02B, CEM-DF12 Volvo P3 – Central Electronic Module LIN-Buss 2 Technical Guide
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CEM-3A00, CEM-1A5F, CEM-1A53 Volvo – CEM Central Module Network Failure Diagnostic Guide
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