This code means that the VDO tachograph is unable to communicate with the DSRC module.
Code 85 is generated when communication between the tachograph head unit and the DSRC (Dedicated Short-Range Communication) module fails. DSRC is used for remote early detection checks by enforcement authorities, allowing certain tachograph data to be read wirelessly without stopping the vehicle.
This fault is only applicable to DTCO 4.0 and 4.1 tachographs and does not affect earlier versions.
The issue is treated as a system communication fault, not a driver-related problem. The tachograph itself may not be defective — the problem can originate from the DSRC module or its connection.
Common causes include:
Communication errors between the tachograph and DSRC unit
Faulty or damaged DSRC components
Wiring or power supply issues affecting the DSRC module
If Code 85 appears, drivers may attempt to turn the vehicle ignition off and back on. If the issue persists, the DSRC system should be checked and any defective components replaced. Because this involves secure tachograph communication systems, the vehicle should be referred to an approved tachograph centre for proper diagnosis and repair.
🔗 Find an approved tachograph centre:
https://www.gov.uk/find-approved-tachograph-centre-atc