What this fault means
VU internal fault means the vehicle unit in your digital tachograph has detected an unexpected error in its program or processes. It can also be linked to blocked buttons, an external communication error, a pulse-output fault or a card-mechanism problem.
Internal fault, vehicle unit fault, means the tachograph vehicle unit cannot be repaired in the cab and must be decommissioned and replaced. According to the official classification, the severity of this fault is Critical.
What to do now
The first steps for a VU internal fault are:
- Acknowledge the message on the tachograph display.
- Have the vehicle unit checked and replaced at an approved workshop.
You may continue driving, but book the workshop immediately. Manual records are required while the tachograph is unserviceable.
If the same fault keeps recurring across several vehicles, tachograph analysis software shows it for the entire fleet in one place.
Your tachograph logs this fault — TAGRA reads it
TAGRA doesn't repair a VU internal fault — the vehicle unit must be decommissioned and replaced by an approved workshop. But once the fault is written to the tachograph's memory and to your driver card, TAGRA finds it in your downloaded data, evaluates it and documents it — exactly what you need at a roadside check and when arranging the replacement with the workshop.
Stop looking up faults by hand — try TAGRA TRUCKER free for 30 daysWhy it happens
According to the manual, a VU internal fault can have several possible causes:
- an unexpected program or process-time error inside the vehicle unit, or
- a button, card mechanism or communication fault, including a blocked button, display link or pulse output fault.
Because this is a fault within the vehicle unit, normal recording cannot be relied on until the tachograph has been replaced.
Can you keep driving?
Yes, but a VU internal fault is classified as a Critical Recording Equipment Fault and the vehicle unit must be decommissioned and replaced. It cannot be repaired in the cab.
Article 37 does not ban driving, but the operator must arrange an approved workshop immediately. Do not wait for the one-week limit: acknowledge the message, check buttons are not jammed and reinsert the card once. If it returns, start manual records and call the workshop. Keep manual records with the driver card while the tacho is unserviceable.
Also displayed as
The same fault appears under several on-screen wordings depending on the tachograph model and firmware. These are the variants recorded in the VDO DTCO 4.1 documentation:
- X⚙ Internal fault — main display wording
- x⚙1 Internal fault — card mechanism (card lock not closed)
- ·° INTERNAL FAULT — symbol notation, section 6.9.13
- DTC 40 00 000C31 — diagnostic trouble code read by a workshop
Related faults
Frequently asked questions
What does Internal fault mean on a tachograph?
Internal fault is a Recording Equipment Fault within the vehicle unit. It indicates an unexpected program or process-time error, or a problem involving controls, communications, pulse output or the card mechanism.
Can I keep driving with a VU internal fault?
Article 37 does not ban driving, but this is critical: book an approved workshop immediately. The vehicle unit must be decommissioned and replaced, so do not wait for the one-week limit.
Does a VU internal fault affect my driver card data?
It can prevent the tacho from recording correctly. While it is unserviceable, make manual records of your name, card or licence number, signature and any periods no longer recorded.
What should I do if Internal fault keeps coming back?
Acknowledge the message, check tacho buttons are not jammed and remove then reinsert the card once. If it returns, begin manual records and call an approved workshop for replacement.