What it means: the tachograph unit itself has broken down or is malfunctioning.
Can you keep driving: yes, but you must log your activity manually from now on.
Deadline for repair: before the vehicle returns to base, or within one week if it can't.
What fault 40 means
Fault 40 is an equipment fault. It doesn't point to your driver card or to a specific sensor, it means the tachograph unit as a whole has stopped working correctly. The regulation that governs this doesn't name individual fault codes, VDO's numbering does, but it does set out exactly what happens next.
The difference with 41
Fault 41 is a card fault, a contact problem between your driver card and the reader. Fault 40 is broader: the device itself is at fault, independent of any card. The obligations that follow are the same either way, but the cause is different, and that matters when a workshop diagnoses it.
Can you keep driving
In the event of the breakdown or faulty operation of a tachograph, the transport undertaking shall have it repaired by an approved fitter or workshop, as soon as circumstances permit. If the vehicle is unable to return to the transport undertaking's premises within a period of one week calculated from the day of the breakdown or of the discovery of defective operation, the repair shall be carried out en route.
Regulation (EU) No 165/2014, Article 37(1). Accessed 26 August 2026.
So yes, you can keep driving. The regulation doesn't ground the vehicle for a broken tachograph, it grounds the vehicle only if you fail to act on it within the deadlines below.
What to log right away
While the tachograph is unserviceable or malfunctioning, the driver shall mark data enabling him to be identified (name, driver card or driving licence number), including a signature, as well as the information for the various periods of time which are no longer recorded or printed out correctly by the tachograph: (a) on the record sheet or sheets, or (b) on a temporary sheet to be attached to the record sheet or to be kept together with the driver card.
Regulation (EU) No 165/2014, Article 37(2).
In practice: your name, your driver card or licence number, a signature, and your driving times and rest periods from the moment the fault appeared. Write it by hand, on a printout if you have one, or on a plain sheet you keep with your driver card.
Who has to fix it, and by when
Repair isn't your personal obligation, it's your transport undertaking's, as the same article states. But the deadline runs from the moment the fault occurred, not from when the paperwork gets sorted: repair as soon as circumstances allow, and within one week if the vehicle can't return to base.
Measures Member States adopt under Article 41 give control officers the power to prohibit further use of the vehicle if the fault isn't fixed within those deadlines. Miss the deadline, and it's no longer just a fine, the vehicle itself can be grounded.
What it costs
The regulation says nothing about price, that's a national and commercial matter. What it does fix is the deadline and the manual record you must keep in the meantime. Keep that written record until you're certain the repair has been logged and accepted, a control officer can still ask for it afterwards.
Also read
Sources
- Regulation (EU) No 165/2014 on tachographs in road transport, Article 37, consolidated version. EUR-Lex
Legal text quoted verbatim from the consolidated English version published on EUR-Lex, accessed 26 August 2026. VDO does not publish an official fault-code glossary in English; the plain-language description above is our own, the legal citation is not.
Stuck? See where there is still room.
Drivers report what they see themselves. Parking full, traffic, hazard, roadworks. Open the app and stop driving alone.