Free used car buyer guide / B9 / B9.5 facelift / 2016-2024
Audi A4 common problems and best years
By BYBA Research - how we score cars
Updated 2026-06-12
BYBA Buy Score
6.1/10
2 walk-away risks, 4 serious faults, 3 minor faults documented for this generation, weighted by severity and repair cost. Biggest factor: passenger occupant detection system airbag recall. Score methodology.
The B9 Audi A4 is a strong used buy when it is treated as an MLB Evo car with expensive cooling, transmission and electronics dependencies, not as a generic compact executive saloon. The costly traps are the EA888 2.0 TFSI coolant pump and thermostat leak, passenger occupant detection recall faults on 2017-2020 cars, S tronic clutch or mechatronic hesitation, B9 hydraulic engine mounts, and diesel SCR/AdBlue repairs on short-trip European cars. The safest money is a 2018-2021 2.0 TFSI quattro with completed 74E3/PODS work, dry carpets, smooth cold S tronic engagement, and a service file that mentions coolant pressure testing. Owners should treat coolant loss, airbag warnings and gearbox shudder as early repair signals rather than "Audi character".
Faults covered
9
Highest risk
Passenger Occupant
Best years
2018-2021
Best buys
- 2018-2021 2.0 TFSI quattro with documented coolant-pump inspection or replacement and no S tronic hesitation.
- Late B9.5 2021-2024 petrol car with clean software/recall status and a registered healthy 12V battery.
- European 2.0 TDI only when motorway use and SCR/AdBlue invoices are present.
Inspect hard
- 2016-2017 launch cars for early electronics, engine mounts, coolant leaks and transmission adaptation.
- Any 2017-2020 A4 sedan/allroad for PODS campaign 74E3 / NHTSA 21V874 completion.
- Any S tronic car that spends its life in city traffic; cold parking-speed behaviour matters more than motorway smoothness.
Avoid
- Cars with repeated coolant top-ups, P00B7/P2181 history, or overheating stories.
- Any airbag/SRS warning on a 2017-2020 car without written Audi campaign proof.
- Diesel cars with AdBlue countdown, DPF warning, or emissions-delete evidence.
Next checks
Before you contact the seller
Check the car's history first. Then bring the right tools if it still looks worth viewing.
Primary next step
Check history, title, and recall status
The faults above matter more if the car also has accident history, finance flags, missing service records, or open safety recalls.
Viewing kit
Bring the right tools
Four cheap tools catch most of the faults on this page at a Audi A4 viewing.
Printable workflow
Take the inspection pack
The PDF is the ordered checklist for the viewing: documents, walk-around, test drive, and scan.
Open PDF optionSome links here are partner links. If you buy through one, BYBA earns a commission. The price you pay does not change. How we make money.
Engines and trims
Which Audi A4 should you buy?
On most used cars, the engine and trim choice changes the risk more than the mileage does. Narrow this down before you start viewing cars.
2.0 TFSI EA888 Gen 3 / Gen 3B
2016-2024
BEST IF COOLING SYSTEM IS CLEAN
This is the main A4 B9 petrol engine and the one most buyers should target. It avoids the older B8 oil-consumption reputation, but it still carries VW Group's plastic coolant pump and thermostat housing problem. A car with a recent genuine or revised pump/housing repair is a better buy than a low-mileage car still on its original leaking assembly.
1.4 TFSI / 35 TFSI EA211
2016-2020 depending market
GOOD LIGHT-USE CHOICE
The small petrol is cheaper to run and less stressed than the high-output 2.0, but it makes the A4 feel more like a comfort commuter than a performance saloon. It is a good fit for buyers who want cabin quality and low running costs; check clutch/S tronic behaviour and service history rather than chasing power.
2.0 TDI EA288
2016-2024 Europe/UK
INSPECT CAREFULLY
The diesel A4 is excellent for long motorway use and poor for short urban ownership. The engine itself is durable when hot and serviced, but SCR, NOx, AdBlue, EGR and DPF parts can turn a cheap diesel into an expensive emissions repair. Buy the usage pattern, not the badge.
3.0 TDI V6
2016-2020 mainly Europe
GOOD IF MAINTAINED
The V6 diesel suits the A4 chassis and quattro drivetrain, but repair access and emissions costs are higher than the four-cylinder diesel. A high-mileage 3.0 TDI with clear AdBlue/DPF history can be a strong car; one with a warning countdown is not a bargain.
S4 3.0 TFSI EA839
2017-2024 petrol in many markets; diesel S4 in parts of Europe
SPECIALIST BUY
The S4 belongs in the A4 family but has a different cost profile. The EA839 V6 is quick and robust when serviced, yet coolant lines, water pump work, turbo-area heat and ZF 8HP servicing make it unsuitable for buyers pricing repairs like a 2.0 TFSI.
Year notes
Year-by-year buyer advice
Use this to narrow the search before you spend time travelling to view a car.
2016
B9 A4 launch year in many markets, on MLB Evo with updated cabin, new electronics architecture and 2.0 TFSI/TDI powertrains.
Buyer: Buy only with a complete service file. The first-year discount is real, but it must pay for coolant inspection, S tronic scan and suspension checks.
Owner: At this age, preventative coolant and gearbox checks matter more than cosmetic upgrades. Keep invoices detailed.
2017
B9 supply broadens; 2.0 TFSI quattro and S tronic become common used-market combinations. PODS recall population begins in North America.
Buyer: This is a good-value year if recall 74E3 is complete and the water pump is dry. Airbag lights are not negotiation items; they are stop signs.
Owner: If your car is in the 2017-2020 PODS group, get campaign proof before selling; it removes a buyer objection.
2018
B9 production matures; most launch build-quality issues are easier to separate from abused examples.
Buyer: One of the better pre-facelift years. Focus on cold S tronic take-up, front suspension knocks and coolant history.
Owner: By now engine mounts and suspension bushes become normal maintenance. Fix them before they make the car feel older than it is.
2019
Late pre-facelift cars in some markets; early facelift/B9.5 timing begins elsewhere.
Buyer: A tidy 2019 can be a sweet spot, but do not assume facelift infotainment or mild-hybrid hardware without checking VIN/spec.
Owner: Keep software and recall printouts with the service book; B9 buyers are now trained to ask.
2020
B9.5 facelift arrives widely with larger touchscreen MMI, revised exterior panels and more mild-hybrid equipment.
Buyer: Check MMI boot/reverse camera behaviour carefully. Later styling is attractive, but software faults can be expensive if modules are blamed.
Owner: Maintain battery health and register any replacement battery; low-voltage faults create misleading MMI and driver-assist symptoms.
2021
Facelift range settles; recall/software populations include rear-view camera and belt/airbag related campaigns depending market.
Buyer: Strong year if all campaigns are closed. Scan the full car, not only the engine ECU.
Owner: Keep every campaign completion sheet; it adds more value than another cosmetic accessory.
2022
Software and emissions/engine-control campaigns appear in NHTSA data for some Audi models.
Buyer: Late cars still need recall lookup. A 2022 with many low-voltage history codes needs battery and gateway diagnosis.
Owner: Do not ignore start-stop unavailable messages; they often precede weak-battery and module-wake complaints.
2023
Late B9.5 production with mature engines but rising complexity in driver assistance and infotainment.
Buyer: Buy condition and warranty status. Accident repair and water ingress matter more than age.
Owner: Preserve warranty claim history and keep scans clean before sale.
2024
Final B9/B9.5 period before the next-generation A5/A4 naming reshuffle in many markets.
Buyer: Pay for a late car only if warranty, recalls and software are clean. A cheaper 2021 can be better if maintained.
Owner: Use remaining warranty for software, camera and coolant concerns now rather than leaving them for the next owner.
Common problems
Faults to check before buying
What fails, what it looks like, what it costs, and the quick checks you can do at the viewing - ranked by how badly each one can hurt you.
Fault 1
EA888 2.0 TFSI coolant pump and thermostat housing leak
Affects
2016-2024 A4 2.0 TFSI, strongest on 2017-2021 cars but every B9 petrol should be checked.
Symptoms
Low coolant warning, sweet smell, pink/white residue, slow warm-up, unstable temperature or cooling-performance codes.
Typical repair cost
EUR 650-1,600; EUR 2,500-5,500+ if overheating damage is present.
Codes / scan clues
P00B7, P2181, P2185-style VAG cooling faults; verify exact code with scan.
Root cause: Plastic pump/thermostat housing and seals warp or seep after repeated heat cycles.
Quick check
- View the car cold and check reservoir level before start.
- Inspect under the intake/front engine area for dried pink coolant.
- Road test until fully warm and confirm stable temperature.
- Ask for an invoice naming water pump or thermostat housing, not vague coolant service.
Buyer note
A dry repaired car is preferable to a low-mileage original that already needs topping up.
Owner note
Pressure-test early; monthly top-ups turn a known EUR 1k repair into engine-risk territory.
Fault 2
Passenger Occupant Detection System airbag recall
Affects
2017-2020 A4 sedan and A4 allroad in NHTSA 21V874 / Audi 74E3 populations.
Symptoms
Passenger airbag OFF when occupied, SRS light, PODS faults or active recall.
Typical repair cost
EUR 0 under recall; EUR 350-1,400 outside campaign/import coverage.
Codes / scan clues
Audi SRS/PODS manufacturer codes; generic OBD is insufficient.
Root cause: PODS wiring/contact fault can disable the passenger airbag.
Quick check
- Run VIN for Audi 74E3 / NHTSA 21V874 completion.
- Sit an adult in the passenger seat and observe airbag indicator behaviour.
- Confirm SRS light self-test goes out and stays out.
- Scan the airbag module before deposit.
Buyer note
Do not buy an A4 with an airbag light on the seller's promise of a cheap reset.
Owner note
Keep the recall completion sheet; it is a safety and resale document.
Fault 3
7-speed S tronic hesitation, shudder or mechatronic wear
Affects
Most 2.0 TFSI/TDI B9 A4 variants with DL382 7-speed S tronic.
Symptoms
Delayed D/R engagement, parking-speed shudder, harsh 1-2 shifts, gearbox warnings or ATF seep.
Typical repair cost
EUR 250-550 service/adaptation; EUR 900-2,200 mechatronic/leak work; EUR 3,000-6,500 major repair.
Codes / scan clues
VAG P17xx or gearbox-specific pressure/adaptation faults; exact scan required.
Root cause: Clutch adaptation wear, valve-body/mechatronic faults, fluid degradation or leaks.
Quick check
- Cold-start and select D then R without throttle.
- Crawl in traffic and reverse uphill.
- Scan the transmission control unit.
- Check for S tronic fluid/adaptation invoices.
Buyer note
Smooth motorway shifts do not prove a good dual-clutch box; low-speed behaviour is the test.
Owner note
Service fluid and investigate leaks early; adaptation cannot hide mechanical wear forever.
Fault 4
Hydraulic engine mount collapse or leakage
Affects
2017-2024 A4 2.0 TFSI/TDI, usually around 60k-120k km.
Symptoms
Idle vibration, thump selecting D/R, engine rocking, oily mount residue.
Typical repair cost
EUR 500-1,200 one mount; EUR 900-2,000 both mounts.
Codes / scan clues
Usually none; active mounts may store manufacturer-specific faults.
Root cause: Fluid-filled mounts split internally or leak after heat and torque cycling.
Quick check
- Watch engine movement while selecting D/R with brake held.
- Feel idle through steering wheel and seat.
- Inspect below mounts for oily staining.
- Do not confuse mount thump with S tronic clutch shudder.
Buyer note
A mount bill is a negotiation item, not a reason to reject an otherwise clean car.
Owner note
Replace tired mounts before they stress exhaust and driveline joints.
Fault 5
Front multi-link suspension arm, bush and wheel-bearing wear
Affects
All B9 A4, worse with S line wheels, rough roads and quattro tyre mismatch.
Symptoms
Knock over small bumps, steering shimmy, inner tyre wear, bearing hum.
Typical repair cost
EUR 250-700 for individual arms/links; EUR 900-2,000 front refresh; EUR 350-800 bearing.
Codes / scan clues
None.
Root cause: Complex multi-link front suspension uses many rubber bushes and ball joints that wear with age and road salt.
Quick check
- Drive slowly over broken road with windows down.
- Inspect inner tyre shoulders.
- Brake from motorway speed and feel for shimmy.
- Ask for alignment printout after suspension work.
Buyer note
Suspension wear is acceptable only when priced; uneven tyres suggest it has been ignored.
Owner note
Refresh arms in pairs/sets and align immediately; piecemeal work gives poor results.
Fault 6
2.0/3.0 TDI SCR, AdBlue, NOx, EGR and DPF faults
Affects
European/UK B9 A4 diesel models, especially short-trip cars.
Symptoms
AdBlue countdown, DPF warning, limp mode, failed emissions test, NOx sensor faults.
Typical repair cost
EUR 350-900 NOx sensor; EUR 700-1,600 AdBlue pump/tank/doser; EUR 900-2,500 EGR/DPF.
Codes / scan clues
P20EE, P204F, P229F, P2002 families; VAG scan required.
Root cause: SCR dosing, NOx sensor ageing, AdBlue crystallisation, EGR fouling and soot/ash load.
Quick check
- Scan engine and SCR modules.
- Check for AdBlue countdown after road test.
- Ask for motorway usage and emissions-system invoices.
- Reject deleted or tampered emissions hardware.
Buyer note
A cheap diesel with an emissions countdown is usually already more expensive than a petrol.
Owner note
Use diesels for long hot runs and repair the first NOx/AdBlue fault before it cascades.
Fault 7
MMI, rear camera and low-voltage software faults
Affects
Mostly 2020-2024 facelift cars, but earlier B9 MMI can also reboot or drain battery.
Symptoms
Black screen, reverse camera missing, CarPlay instability, repeated low-voltage faults.
Typical repair cost
EUR 0 recall/software; EUR 150-350 update/diagnosis; EUR 800-2,500 module.
Codes / scan clues
Gateway, infotainment and battery-management codes; exact VAG codes vary.
Root cause: Software level, module wake faults, weak or uncoded 12V battery, camera/display campaigns.
Quick check
- Start car twice and time MMI boot.
- Select reverse several times.
- Pair a phone and test CarPlay/Android Auto.
- Scan full vehicle for low-voltage history.
Buyer note
A late A4 with a glitchy screen is not automatically harmless; modules are expensive.
Owner note
Replace and register batteries properly before chasing phantom MMI faults.
Fault 8
Cold-start timing-chain or tensioner noise
Affects
Higher-mileage early 2016-2017 EA888 B9 cars; lower confidence than older B8 failures.
Symptoms
Rattle longer than 1-2 seconds cold, extended crank, cam/crank faults.
Typical repair cost
EUR 900-2,200 chain/tensioner service; EUR 3,500-7,000+ if timing jumps.
Codes / scan clues
P0011, P0016 and related VAG cam/crank correlation codes.
Root cause: Chain/tensioner wear or oil-pressure bleed-down on neglected cars.
Quick check
- Insist on first start of the day.
- Record engine-bay startup audio.
- Review oil intervals for long-life abuse.
- Scan for cam/crank correlation faults.
Buyer note
Do not buy a pre-warmed early B9 that rattles on the second start.
Owner note
Short oil intervals are the cheapest protection for chain and turbo hardware.
Fault 9
12V mild-hybrid and battery registration problems
Affects
2020-2024 B9.5 mild-hybrid petrol/diesel cars and any older B9 with weak battery.
Symptoms
Start-stop unavailable, low battery warning, no-start after sitting, random assistance faults.
Typical repair cost
EUR 250-550 battery/registration; EUR 700-1,800 charging-system diagnosis.
Codes / scan clues
Energy-management, generator and gateway voltage codes.
Root cause: Weak battery, replacement not coded, MHEV charging issue or module wake fault.
Quick check
- Check battery date label.
- Verify replacement battery was coded.
- Scan full car for undervoltage storms.
- Confirm start-stop after a long road test.
Buyer note
A weak battery can make a good A4 look broken, but repeated module faults need diagnosis.
Owner note
Code the battery replacement; uncoded batteries shorten module life and confuse diagnostics.
Inspection pack
Printable checklist for the viewing
The free page helps you decide whether the car is worth seeing. The paid guide is the ordered, printable checklist you use at the car.
- Audi recall/campaign printout, especially 74E3/PODS for 2017-2020 cars.
- Coolant pump, thermostat, pressure-test or coolant-leak invoices.
- S tronic service/adaptation records.
- Battery replacement and coding invoice on 2020+ cars.
- Check coolant level cold and inspect undertray area for pink residue.
- Inspect tyres for matching sizes and inner-edge wear.
- Look for damp carpets, boot moisture and windscreen replacement clues.
- Confirm SRS light self-tests and stays off.
- Boot MMI twice and test reverse camera.
- Pair phone and test infotainment controls.
- Cold D/R engagement and low-speed S tronic crawl.
- Broken-road suspension knock check.
- Full warm-up temperature stability check.
- Full VAG scan: engine, gearbox, SRS, gateway, infotainment.
- Look for P00B7/P2181 cooling, P17xx gearbox and undervoltage history.
Bottom line
Buy: A 2018-2021 2.0 TFSI quattro with clean PODS recall status, dry coolant system, smooth S tronic cold behaviour and detailed service invoices.
Avoid: Any A4 with active airbag warning, repeated coolant loss, AdBlue countdown, harsh dual-clutch engagement or seller-cleared low-voltage fault storms.
Quick answers
Audi A4 buyer questions
The short versions of what this page answers in full.
What are the most common Audi A4 2016-2024 problems?
The highest-impact documented faults are: EA888 2.0 TFSI coolant pump and thermostat housing leak; Passenger Occupant Detection System airbag recall; 7-speed S tronic hesitation, shudder or mechatronic wear. This guide covers 9 faults in total, each with symptoms, typical repair costs, and checks you can do at a viewing.
Which Audi A4 years are the best to buy?
2018-2021 stand out in this generation. A 2018-2021 2.0 TFSI quattro with clean PODS recall status, dry coolant system, smooth S tronic cold behaviour and detailed service invoices.
Which Audi A4 should I avoid?
Any A4 with active airbag warning, repeated coolant loss, AdBlue countdown, harsh dual-clutch engagement or seller-cleared low-voltage fault storms.
Is the Audi A4 2016-2024 a reliable used buy?
BYBA scores it 6.1/10 (buy with checks). 2 walk-away risks, 4 serious faults, 3 minor faults documented for this generation, weighted by severity and repair cost. Biggest factor: passenger occupant detection system airbag recall.
Get updates when this guide changes
Recalls get added, repair costs shift, and new fault patterns show up in the data. Leave an email and we'll tell you when the Audi A4 guide gets a meaningful revision. Nothing else, no selling your address.
Research basis
- NHTSA recall lookup
- NHTSA/Audi 74E3 PODS recall PDF
- OEMDTC 74E3
- Four Rings Repair B9 A4
- CarComplaints 2017 A4 coolant
- Go-Parts EA888 pump guide
- Audizine B9 common issues
- Paul Tan B9 facelift
- Audi owner discussion
- Audi A4 engine listing
- Diesel emissions codes background
- What Breaks Audi A4 B9 notes
- Audi owner timing-chain discussion