Thinking about buying a used Audi S4 (2001–2016) in New Zealand? We've documented 10 known faults for this model spanning transmission, engine, cooling, and suspension. Each researched and verified before it's published. The most serious issues here are rated critical. Two are set out in full below — the rest, with the symptoms, repair costs and checks for each, are free with an account.
10
Documented faults
Critical
Most serious
$550–$2,000
Typical repair
5
Systems covered
Known Audi S4 faults
Every fault below is documented specifically for this model — researched and verified before it’s published.
01S-Tronic DL501 Mechatronic Unit Failure
CriticalCommonTransmission $3,000–$8,000 to fix
The 7-speed S-tronic dual-clutch transmission (DL501 / 0B5 code) used longitudinally in the A4 pairs a wet multi-plate clutch pack with an electro-hydraulic mechatronic control unit. The mechatronic valve body develops internal hydraulic leaks and solenoid faults causing shuddering at low speed, harsh or refused gear engagement, and in severe cases complete loss of drive. Clutch pack wear also produces juddering when pulling away from rest. Audi extended the warranty in some markets but units outside warranty require full replacement. B9 variants retained DL501 and share the same failure mode.
Symptoms to notice
Shuddering or vibration when pulling away at low speed
Harsh, jerky downshifts especially in traffic
Transmission warning light or failsafe mode
Delayed or refused engagement from Park or Neutral
What to check
Test drive in slow stop-start traffic and note any shuddering when pulling away from rest. Perform multiple low-speed creep manoeuvres. Check for stored transmission fault codes (P17BF, P175B, P1717 are common mechatronic codes on DL501). Confirm the mechatronic oil (Haldex/DSG fluid) has been serviced at recommended intervals. Ask if Audi extended warranty work was carried out.
Where to look: Transmission housing, mechatronic unit on left side of gearbox
Ask the seller
“Has the S-tronic mechatronic unit ever been replaced or remanufactured?”
“Has S-tronic fluid been changed at the Audi-recommended interval?”
“Has the transmission ever been in failsafe or warning mode?”
02MMI 2G/3G Display and Control Unit Failure
MinorCommonElectrical $400–$2,800 to fix
The B8 A4 introduced Audi's MMI (Multi Media Interface) infotainment system in both 2G and 3G hardware generations. The display module uses a TFT screen with ribbon cable connections that are prone to fatigue cracking from repeated thermal cycling and vibration. Failure typically presents as vertical pixel lines, partial blackouts, or a completely black screen while the audio and navigation systems continue to function (confirming the processor is running but the display has failed). In other cases the control unit itself fails — the MMI becomes unresponsive to inputs, reboots continuously, or loses stored settings after ignition cycles. The 3G MMI navigation hard drive can also fail, causing the satellite navigation to become unavailable while the rest of the unit continues to operate.
Symptoms to notice
Vertical or horizontal lines of dead pixels across the display, or a partially or fully black screen while audio continues to play
MMI system freezing mid-operation, becoming unresponsive to rotary controller or button inputs
Spontaneous MMI reboots — the Audi rings boot screen appears repeatedly during a journey
Navigation system unavailable or showing an error message while radio and phone functions continue to operate
What to check
Switch on the ignition and inspect the MMI display for missing pixel columns, discolouration, or partial blackout — these are characteristic of ribbon cable failure. Cycle through all MMI menus to check for freezing or sluggish response. Test the navigation system — a failed hard drive will show an error or fail to load maps. Check that the MMI retains settings (radio stations, navigation home address) after the car is locked and reopened. Inspect the screen edges for separation or any signs that the unit has been previously opened.
Where to look: Centre stack dashboard (display screen) and boot-mounted MMI control unit/hard drive
Ask the seller
“Does the MMI display show any lines, dark patches, or go black at any point?”
“Does the MMI ever freeze or reboot itself during a drive?”
“Is the satellite navigation fully functional, including map loading?”
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8 more documented faults on the Audi S4
Symptoms, what to check, where to look and what to ask the seller — for every fault above. Free with an account, no card needed. One account covers one vehicle, so make it the car you’re actually looking at.
This page covers the model. Enter the plate of the actual car you’re looking at and see its year, engine, safety rating and register flags — free, no account needed.
Like any used car, it depends on the specific example and its service history. Across the 10 documented faults for the Audi S4, the recurring problem areas are transmission, engine, and cooling. A Audi S4 with a full service history and no signs of the issues listed on this page can be a sound buy but each one needs to be checked individually before you commit.
What are the most common problems with a used Audi S4?
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We've catalogued 10 known faults for the Audi S4, covering transmission, engine, and cooling. Two are written out in full on this page. The rest — with the symptoms to notice, what to inspect, and typical repair costs for each — are free once you create an account.
How much do repairs cost on a Audi S4?
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Most single repairs on the Audi S4 fall between $550–$2,000 at NZ independent-workshop rates. Some of the 10 documented faults cost less and a few cost considerably more, and no one car needs them all. Knowing which ones to look for before you view is what lets you negotiate the price down or walk away.
Should I get a pre-purchase inspection on a Audi S4?
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Yes. A Audi S4 inspection focused on its known weak points is the single best way to avoid an expensive mistake. KickTyres gives you a guided, model-specific inspection plus a market valuation and negotiation figure for $17.90 far less than the cost of missing one of the faults on this page.