IsItAGoodCar
Reliability Guide

Common Problems with the
2021 Audi A6 Mk5 (C8)

We've identified 5 known issues that can affect the 2021 Audi A6 Mk5 (C8). 3 of these are serious faults that could be expensive to repair.

5
Known Issues
3
Serious
2
Moderate
0
Minor

All Known Issues

Belt Starter Generator (BSG) Failure

SeriousElectrics & Electronics

The 48V mild-hybrid system can fail, leading to an "Electrical system: fault" message.

Est. Repair Cost: £0–£1,500
Warning Signs:

Warning messages, Total electrical failure while driving

What to Inspect:
  • Check Audi recall database for "48V BSG" campaign
  • Ask for evidence the starter-alternator recall (R/2020/138 / R/2020/265) has been completed
Verified by IsItAGoodCar Research TeamUpdated
Official Recalls & Reference Documents:

DL382 S tronic Gear Selection / Mechatronic Faults

SeriousGearbox & Transmission

Control or clutch faults can interrupt gear selection. Identify the gearbox code first: this entry applies to the longitudinal DL382 family, not every automatic sold under the same model name.

Warning Signs:

Gearbox warning, Delayed engagement or missing gears

What to Inspect:
  • Test drive from cold and again when warm
  • Check gearbox-specific service invoices and obtain a diagnostic report
Verified by IsItAGoodCar Research TeamUpdated

TDI AdBlue / NOx Sensor Faults

SeriousExhaust & Emissions

SCR dosing or NOx sensor faults can trigger an emissions warning and a no-restart countdown. Adding fluid alone does not resolve every system fault.

Warning Signs:

AdBlue system fault, No-restart countdown

What to Inspect:
  • Check stored faults and repair invoices
  • Have dosing pressure and NOx readings checked before replacing parts
Verified by IsItAGoodCar Research TeamUpdated

Dual MMI Touch Response Screen Freezing & Blackouts

ModerateElectrics & Electronics

The dual upper (navigation/media) and lower (climate/haptics) touchscreen displays can fail to initialize, suffer touch input lag, or reboot randomly while driving.

Est. Repair Cost: £0–£650
Warning Signs:

Lower climate screen unresponsive to haptic touch, Upper display freezes on Audi logo, Reversing camera image flickers

What to Inspect:
  • Test both touchscreens through multiple submenus
  • Verify MIB3 software version is above 3241
Verified by IsItAGoodCar Research TeamUpdated

2.0 TDI / 3.0 TDI Coolant Regulation Valve & Water Pump Weepage

ModerateCooling System

Electrically controlled coolant regulator shut-off valves and vacuum-actuated water pump plastic housings develop weeping leaks, coating the front of the block in crusty pink residue.

Est. Repair Cost: £380–£850
Warning Signs:

Low coolant warning chime, Coolant level steadily drops over 1,000 miles, Faint sweet smell from engine bay

What to Inspect:
  • Inspect lower undertray and engine front for pink coolant crust
  • Verify expansion tank pressure seal
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 2021 Audi A6 Mk5 (C8)

  • Ensure the Belt Starter Generator (BSG) recall has been performed
  • Check both touchscreens for responsiveness
  • Verify AdBlue and NOx sensor health
Check a 2021 Audi A6 Mk5 (C8) by Registration