IsItAGoodCar
Reliability Guide

Common Problems with the
2017–2019 Audi A4 Mk5 (B9)

We've identified 4 known issues that can affect the 2017–2019 Audi A4 Mk5 (B9). 2 of these are serious faults that could be expensive to repair.

4
Known Issues
2
Serious
2
Moderate
0
Minor

All Known Issues

AdBlue SCR System NOx Sensor & Tank Heater Failure

SeriousExhaust & Emissions

On 2.0 TDI and 3.0 TDI diesel models, failing downstream NOx sensors or crystallized AdBlue dosing injectors trigger a persistent dashboard no-restart countdown.

Est. Repair Cost: £450–£1,200
Warning Signs:

"AdBlue: No restart in 650 miles" warning, Engine management light on, Failure to clear after topping up DEF fluid

What to Inspect:
  • Check AdBlue tank filler neck for white crystal deposits
  • Scan for NOx sensor heater circuit fault codes
Verified by IsItAGoodCar Research TeamUpdated

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

Water Pump / Thermostat Leaks

ModerateCooling System

Later petrol and diesel engines still suffer coolant leaks from pumps or plastic thermostat housings.

Est. Repair Cost: £350–£750
Warning Signs:

Low coolant warning, Pink residue around front of engine

What to Inspect:
  • Check coolant level cold
  • Look for recent cooling-system repair invoices
Verified by IsItAGoodCar Research Team

Front Suspension Multi-Link Upper Control Arm Bushing Wear

ModerateSuspension & Chassis

The five-link front suspension utilizes rubber-metal hydro-bushings on the upper control arms that crack and tear, leading to vague high-speed steering and knocking over potholes.

Est. Repair Cost: £280–£600
Warning Signs:

Knocking noise when braking over uneven surfaces, Uneven front tyre inner edge wear, Steering wander on rutted motorways

What to Inspect:
  • Pry control arms to check for excessive play
  • Inspect rubber boots for oil weeping from hydro-bushings
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 2017–2019 Audi A4 Mk5 (B9)

  • ✓Check virtual cockpit, MMI and reversing camera thoroughly
  • ✓TDI buyers should watch for NOx-sensor and AdBlue faults
  • ✓S tronic cars should feel clean and decisive
20162020
Check a 2017–2019 Audi A4 Mk5 (B9) by Registration