This code means that the tachograph has detected that its power supply has dropped or risen outside the normal operating range.
Common causes include:
– Loose or poor electrical connections
– Voltage drop during engine start
– Wiring or power supply faults
A voltage interruption can affect recorded data and may raise compliance concerns if it happens repeatedly. It should never be ignored, especially if the vehicle is experiencing other electrical issues.
Drivers should:
– Report Code 31 to the transport office immediately.
– Make a note of when it appears (for example, during engine start).
– Avoid continuing to operate the vehicle if there are ongoing electrical problems.
Operators can arrange for basic vehicle checks such as:
– Visible damage to the plug and cable
– Obvious loose connections
Any detailed electrical testing or tachograph-related repairs must be carried out by an approved tachograph centre.
If the warning persists after basic vehicle checks, the vehicle should be booked into an approved tachograph centre for proper inspection and testing.
🔗 Find an approved tachograph centre:
https://www.gov.uk/find-approved-tachograph-centre-atc