IsItAGoodCar
Reliability Guide

Common Problems with the
2020 Audi A4 Mk5 (B9)

By 2020 the B9 had received a facelift with updated styling and improved engines. Water pump leaks remain the primary concern but are better understood. This is generally the safest used B9 buy.

What changed for 2020

  • •Facelift with revised headlights and grille
  • •Updated engine range with improved efficiency
  • •Revised MMI software
  • •Enhanced driver-assistance features

Common MOT watch-outs

  • !Water pump leaks remain possible
  • !LED DRL failures still occur
  • !DPF issues on town-driven diesels
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 2020 Audi A4 Mk5 (B9)

  • Facelift cars with documented water-pump history are the best buys
  • Check all LED lighting functions during inspection
  • Ensure all software updates have been applied
2017–20192021–2024
Check a 2020 Audi A4 Mk5 (B9) by Registration