IsItAGoodCar
Reliability Guide

Common Problems with the
2019–2021 Audi A8 Mk4 (D5)

We've identified 4 known issues that can affect the 2019–2021 Audi A8 Mk4 (D5). 3 of these are serious faults that could be expensive to repair.

4
Known Issues
3
Serious
1
Moderate
0
Minor

All Known Issues

48V Belt-Starter Generator (BSG) Failure

SeriousElectrics & Electronics

The Continental BSG power transistors overheat and fail, causing the 48V system to shut down and eventually leaving the car stranded.

Est. Repair Cost: £0 (recall) – £2,500
Warning Signs:

Multiple electrical system warnings, Start-stop inactive, Car immobilised after standing

What to Inspect:
  • Verify service campaign 27BQ has been completed via VIN
  • Check for electrical system warnings on startup
  • Ask for BSG replacement invoice
Verified by IsItAGoodCar Research Team

Air Suspension Strut Leaks

SeriousSuspension & Chassis

The standard adaptive air suspension develops leaks over time, causing uneven ride height and expensive compressor replacement.

Est. Repair Cost: £800–£3,000
Warning Signs:

Car sitting low on one corner, Compressor running constantly, Level-control warning

What to Inspect:
  • Check ride height before engine start
  • Cycle through height settings
  • Listen for compressor strain
Verified by IsItAGoodCar Research Team

TDI SCR / AdBlue System Faults

SeriousExhaust & Emissions

Diesel versions with SCR can develop dosing, heater or NOx sensor faults. A system fault may lead to a no-restart countdown even with sufficient AdBlue; diagnosis should distinguish fluid level from component failure.

Warning Signs:

AdBlue system warning, No-restart countdown

What to Inspect:
  • Check warning history and emissions repair invoices
  • Request a diagnostic check of dosing pressure, heater operation and NOx readings
Verified by IsItAGoodCar Research TeamUpdated

Dual-Touchscreen MMI Freezes

ModerateElectrics & Electronics

Both the upper and lower MMI screens can freeze, go black, or reboot, affecting navigation, climate and seat controls.

Est. Repair Cost: £0–£2,500
Warning Signs:

Upper screen going black, Lower climate screen unresponsive, Spontaneous system reboots

What to Inspect:
  • Test both screens extensively
  • Try a 15-second power button reset
  • Check for pending software updates
Verified by IsItAGoodCar Research Team

Buying Tips for 2019–2021 Audi A8 Mk4 (D5)

  • ✓Check for any warning lights related to the 48V electrical system; failures of the Belt Starter Generator (BSG) are common, expensive, and will leave the car completely immobilized.
  • ✓Test the dual-screen MMI system extensively for lag, freezing, or haptic feedback failures, as software bugs are frequent and may require dealer updates.
  • ✓Ensure the predictive active air suspension (if optioned) functions correctly without warning lights; it is incredibly complex and uses cameras to read the road ahead.
  • ✓Inspect the huge alloy wheels for damage and verify the condition of the tyres, as they are acoustically insulated and very expensive to replace.
  • ✓Check the operation of the dynamic all-wheel steering at low speeds; it should turn smoothly without groans or clunks from the rear axle.
  • ✓Verify the interior trim, particularly the motorized air vent covers, which can fail to open or close smoothly due to weak motors.
20182022
Check a 2019–2021 Audi A8 Mk4 (D5) by Registration