Audi A4 B6 2002-2006 (2nd Generation) Review

Everything You Need To Know Before Buying A Used A4 2nd Gen

Read in this article:

2nd Gen Audi A4: What Owners Say

  • Owners love the A4's looks inside and out, and the excellent build quality.
  • Comfort and ride quality are praised by both drivers and passengers.
  • Long features list adds to the "downsized luxury" appeal.
  • Can be very costly to maintain.
  • Most families find the rear seating area a bit snug.
  • Electrical problems appear seemingly at random, and usually cost a lot to repair.

Second Generation Audi A4 Sedan Facelift

The Audi A4 B6 had a comparatively short production life, and was replaced by the heavily revised B7 generation in 2006. Consequently, there wasn't really time for Audi to perform any mid-life surgery on the B6 model.

2002-2006 A4 B6 Front View Audi
2002-2006 A4 B6 Front View
2002-2006 A4 B6 Rear View Audi
2002-2006 A4 B6 Rear View
2004-2006 A4 B6 Side Changes CarBuzz
2004-2006 A4 B6 Side Changes

The 2004 model year brought a new wheel design to the base 1.8T model, moving up one size with 16-inch alloys instead of the 15-inch wheels used before1.

2004-2006 A4 B6 Interior Changes CarBuzz
2004-2006 A4 B6 Interior Changes

Inside the 2004-2005 Audi A4, you'll find a redesigned steering wheel1 and, on vehicles equipped with the optional navigation system, a larger color display screen (up from five to 6.5 inches).

Engine, Transmission and Drivetrain

Audi offered two engines for the A4 B6 in the North American market, matched to an array of gearboxes and drivetrain options. The base engine is an intercooled 1.8-liter turbo unit with 20 valves, which is mated to either a five-speed manual transmission or a CVT (Multitronic) in FWD trim, or with a five-speed manual or five-speed torque-converter automatic (Tiptronic) when specified with AWD.

From 2004, all manual quattro-equipped A4 1.8T models dropped the five-speed and gained a new six-speed manual in its place, but the five-speed unit remained for the basic FWD Audi A4 sedan until 2005, after which it also switched to a six-speed gearbox. The 3.0 models were available with FWD but only equipped with the CVT; or AWD, with either a six-speed manual or five-speed Tiptronic transmission.

1.8L Inline-4 Gas Turbocharged DOHC AMB
168 hp | 166 lb-ft
168 hp
166 lb-ft
Five-/six-speed manual, five-speed automatic, or Multitronic CVT

The second-generation Audi A4's base engine is a carry-over from the first-generation model, and has been used in a legion of other Volkswagen Group vehicles as well. The most notable features on this engine are variable valve timing on the intake cam, and a five-valves-per-cylinder design for the cylinder head.

A toothed belt drives the exhaust cam, from where a small chain at the back of the engine powers the intake cam. It's a rugged engine, but there are two critical preventative maintenance items that need to be kept up to date to ensure a long life. Cambelt changes need to be performed on schedule, and the engine oil sump periodically needs to be cleaned of oil sludge. Keep these items on your maintenance list, and an Audi 1.8T will be capable of reaching an intergalactic mileage.

3.0L V6 Gas DOHC AVK
217 hp | 221 lb-ft
217 hp
221 lb-ft
Six-speed manual, six-speed automatic, or Multitronic CVT

This is the upgrade engine option for the Audi A4 B6, and shares many features with the 1.8T base engine. It also employs five valves per cylinder and a belt-driven camshaft setup, and expands the variable valve timing to the exhaust cams as well.

As with the 1.8T, this engine really only needs regular cambelt replacements and the periodic sump service to provide a good service life, but is otherwise remarkably free of serious design flaws.

2002-2006 Audi A4 B6 Real MPG

In recent years, owners have been able to upload their real-world fuel consumption figures to the EPA website to create a database of real-world fuel efficiency for US-market vehicles. Some Audi A4 B6 owners have added their information to this database to obtain relevant real-world figures, but these serve only as a rough guide as to what range of real-world consumption is possible, because these figures were not obtained using the EPA's carefully observed testing procedures.

EPA mpg (city/highway/combined)Real-world combined mpg*
1.8T five-speed manual FWD sedan (2002-2005)20/29/2327.5
1.8T six-speed manual FWD sedan (2005)20/31/24N/A
1.8T CVT FWD sedan (2002-2005)20/27/2327.1-29.4
1.8T five-speed manual AWD sedan (2002-2003)18/26/2125.7-26.1
1.8T six-speed manual AWD sedan (2004-2005)19/27/2224.9-27.4
1.8T five-speed manual AWD sedan (2002-2005)17/26/2019
1.8T five-speed automatic AWD sedan (2002-2005)18/26/2120.6-22.6
1.8T five-speed manual AWD Avant (2002-2003)18/26/21N/A
1.8T five-speed automatic AWD Avant (2002-2005)18/26/2118.4-22.9
1.8T six-speed manual AWD Avant (2004-2005)19/28/2226.6
1.8T, CVT, FWD Cabriolet (2003-2006)20/28/23N/A
3.0 CVT FWD sedan (2002)17/25/1923.9
3.0 CVT FWD sedan (2003-2004)18/26/21N/A
3.0 CVT FWD sedan (2005)19/26/22N/A
3.0 six-speed manual AWD sedan (2002-2003)16/23/1819.1-21.4
3.0 six-speed manual AWD sedan (2004-2005)16/24/1927.5
3.0 five-speed automatic AWD sedan (2002-2005)16/24/1920.6-22
3.0 five-speed manual AWD Avant (2002-2003)16/23/1822.1
3.0 six-speed manual AWD Avant (2004-2005)16/24/19N/A
3.0 five-speed automatic AWD Avant (2002)16/23/19N/A
3.0 five-speed automatic AWD Avant (2003-2005)16/24/19N/A
3.0 CVT FWD Cabriolet (2003-2004)18/25/21N/A
3.0 CVT FWD Cabriolet (2005)18/26/21N/A
3.0 five-speed automatic AWD Cabriolet (2004)16/23/19N/A
3.0 six-speed automatic AWD Cabriolet (2005)18/25/21N/A
3.0 six-speed automatic AWD Cabriolet (2006)16/23/18N/A

* Real-world mpg and MPGe figures are provided by the EPA. Once a car has been on sale for a significant period of time, the EPA gets real-world figures directly from the customer base. These figures are then provided on the EPA website. Real-world figures are not available for certain models due to a lack of sales, or not enough people partaking in this after-sales survey.


The Audi A4 B6 was regarded as a very safe car in its era, and features a safety kit list which still appears up to date two decades on. Standard safety equipment on all variants includes four-wheel disc brakes (ventilated in front), with ABS and electronic brakeforce distribution; traction and stability control; six airbags (two frontal, two side-impact, and two curtain airbags), seatbelt pretensioners front and rear, child seat anchors at the rear, and height-adjustable head restraints all round.

NHTSA crash tests confirm that the B6 Audi A4 is indeed very safe, but it must be noted that this testing was performed under the pre-2011 NHTSA protocol, which was less stringent than the current standards demand. This means that these results can not be directly compared to post-2011 test results.

Frontal impact testing earned the Audi A4 B6 four stars for both driver and front passenger protection, side-crash testing netted five stars for front-occupant protection and four stars for rear-occupant protection, and four stars were allocated for rollover protection. These ratings apply to the sedan and Avant body styles but won't be valid for the convertible - the NHTSA never tested an Audi B6 convertible, and, while its frontal protection should equal that of the sedan, the convertible's side-impact and rollover protection obviously won't be as good as those of its hard-roofed siblings.

US NHTSA Crash Test Result Audi A4 Sedan and Avant (2005)

Frontal Barrier Crash Rating (Driver):
Frontal Barrier Crash Rating (Passenger):
Side Crash Rating (Front):
Side Crash Rating (Rear):
Rollover Rating:

Audi A4 B6 Trims

The Audi A4 2nd generation arrived in 2002 with a selection of two body types, sedan and Avant, with the A4 B6 convertible arriving for 2003 and continuing until 2006. Each body style could be ordered with either engine and with a selection of gearboxes, while quattro AWD was fitted as standard on all Avant models but optional on the sedan. The convertible was available in 1.8T Multitronic, 3.0 Multitronic, or 3.0 quattro automatic format, but no manual gearbox was offered for this body style, regardless of engine choice.

One special Audi A4 B6 model was produced for the US market. Available from 2004 onwards, the "Ultra Sport" package was essentially the forerunner of the "S line" trim which would feature on the next-generation Audi A4 B7. It included the 18-inch alloy wheels, which were first used on the B5-generation RS4, along with a lower and stiffer suspension, front and rear spoilers, and more aggressive side skirts. All engines, bodies, and transmissions could be ordered with the Ultra Sport trimmings.


The most basic Audi A4 B6 is equipped with a wide array of standard comfort and convenience features, with cloth-upholstered sports seats and a leather-trimmed steering wheel and shift knob, manual tilting and telescoping steering-wheel adjustment, heated exterior mirrors with power adjustment, remote power door locks, one-touch power windows all round, a 150-watt audio system with ten speakers and a six-disc in-dash CD changer, cruise control, dual-zone climate control with activated-carbon air filtration, 15-inch alloy wheels, and front reading lights all part of the baseline features list.


Upgrading from a 1.8T to a 3.0 not only gives you the larger engine, but also adds some more standard goodies to the specification sheet, with 12-way power adjustment for both the driver and the front passenger, and 16-inch alloy wheels being the headline feature. On top of this, buyers could add niceties such as wood cabin trimmings, upgraded leather upholstery, an electric opening and sliding glass sunroof, seat memory functions, firmer suspension, and sportier 17- or 18-inch alloy wheels.

Second Generation Audi A4 Sedan, Avant, and Cabriolet Features

1.8T3.01.8T quattro3.0 quattro
Bluetooth ConnectionON/AN/AO
Heated Front Seat(s)OOOO
Heated Rear Seat(s)OOOO
Navigation SystemOON/AO
Power Driver SeatON/AON/A
Power Mirror(s)N/AON/AO
Power Passenger SeatON/AN/AN/A
Premium Sound SystemOOOO
Rear Parking AidOON/AO
Rear Side Air BagOOOO
Satellite RadioOOOO
Seat MemoryN/AON/AO
Steering Wheel Audio ControlsN/AON/AO
Tire Pressure MonitorOON/AO
Universal Garage Door OpenerOOOO

Interior, Trim And Practicality

A4 B6 Interior Overview Audi
A4 B6 Interior Overview

Stepping inside the A4 B6's cabin reveals traditional Audi assembly quality, albeit by now dimmed somewhat by the ravages of time. The cabin's design is ergonomically sound, and most of the trimmings can look very good for many years, but details such as the switchgear's rubberized coating rubbing off will betray the age of almost every Audi A4 B6 out there.

The Audi A4's cabin is a nice place to spend time, though, with very comfortable seats and enough room to keep the front-seat occupants happy, even on long trips. Front headroom of 38.4 inches and shoulder room of 55.1 inches are similar to those of the BMW E46 3 Series, but there's actually fractionally less front legroom in the Audi.

The rear-seat passengers will be less pleased, though, because leg- and headroom are both surprisingly tight, considering the B6 Audi A4's overall size. In fact, the Audi sedan's rear seats have considerably less room all-round than the BMW E46 does. The convertible is even more cramped at the back, and won't comfortably accommodate two average-sized adults on the rear bench.

The A4 Avant B6 solves the rear headroom problem, however, and it's by far the most versatile model in the range. This body style not only liberates more rear headroom, but also boosts luggage capacity from the sedan's 13.4 cu.ft. to 27.8 cu.ft. with all seats in place. Drop the rear seats, and the Avant's cargo hold grows to 59 cu.ft.

1.8T3.01.8T quattro3.0 quattro
Cloth SeatsOOON/A
Leather SeatsOOON/A
Leather Steering WheelOOOO
Premium Synthetic SeatsOOON/A
Vinyl SeatsOOON/A
Woodgrain Interior TrimN/AN/AN/AN/A
Premium Leather SeatsN/AN/AN/AN/A
Leather Seating SurfacesN/AN/AN/AS
Premium Leather Seat TrimN/AON/AO
Leather Seat TrimN/AON/AO
Premium Leather Upholstery Sport SeatsN/AON/AO
Leather Seat InsertsSSSS
Cloth Seat TrimSSSS
Perforated Leatherette Seat TrimSSSS

2002-2006 2nd Gen Audi A4 Sedan, Avant, and Cabriolet Maintenance and Cost

The Audi A4 B6 isn't a particularly problematic vehicle to service and maintain unless something big goes wrong, and except for the fact that both Audi A4 engine derivatives need to be rigorously maintained. Replace the engine oil with good-quality synthetic oil every 5,000 miles and change the filter at the same time. Good-quality oil is the lifeblood of an Audi engine, and compromising on this will lead to tears.

For vehicles equipped with the Multitronic CVT, a transmission oil change and filter replacement every 30,000 miles are required to give it the best chance at survival. The five-speed automatic transmission in the 1.8T quattro and the six-speed automatic in the 3.0 quattro are both capable of a fair service life, provided their transmission fluid and -filters are replaced every 60,000 miles at the latest.

Spark plugs should be replaced every 40,000 miles according to the 2002 Audi service schedule, but we'd recommend replacing them every 30,000 miles instead. Doing so should make it easier for the failure-prone ignition coils to provide a stronger spark for a longer distance. Ensure that the heat range of the spark plugs are as prescribed by Audi, because fitting inappropriate spark plugs could lead to pre-ignition and, consequently, internal engine damage.

The engine air filter also has a 40,000-mile replacement interval, but don't hesitate to shorten this to 30,000 if your vehicle is operated in dusty or polluted conditions. Pollen filter replacement intervals are set at 20,000 miles, and the same advice regarding dusty conditions applies.

Second Gen Audi A4 Basic Service

The Audi A4 1.8T needs 4.3 quarts of 5W-40 full-synthetic oil, which will cost between $73 and $91, including a replacement oil filter. The A4 B6 3.0 has an oil capacity of 6.9 quarts, which will cost between $104 and $147 with a new oil filter.

OEM engine air filters will cost around $29 for both 1.8T and 3.0 engines because they use the same air-filter elements, and their pollen filters are identically priced at $23 for the same reason. As mentioned earlier, spark-plug quality is critical on both the 1.8T and 3.0 engines, so always stick to the manufacturer's specifications here. A set of four OEM spark plugs for the 1.8T will cost about $64, and the correct OEM spark plugs for a 3.0 will amount to around $104.

2nd Generation Audi A4 Tires

Tire Size::
Wheel Size::
16" x 7"
Spare Tire::
Tire Size::
Wheel Size::
16" x 7"
Spare Tire::
1.8T quattro
Tire Size::
Wheel Size::
15" x 7.0"
Spare Tire::
3.0 quattro
Tire Size::
Wheel Size::
16" x 7"
Spare Tire::

Check Before You Buy

There was a number of 2002-2006 Audi A4 recalls over the years, but they were fairly minor in nature and easy enough to rectify. The first recall relates to 2002 and 2003 Audi A4 fuel pump problems on both 1.8T and 3.0 models, which may fail due to an electrical problem, causing the car to stall. The remedy is for an Audi dealership to fit a new fuel pump, so check that this recall has been performed.

2003 and 2004 Audi A4s with xenon headlights were also subject to a recall, where the xenon reflectors may deteriorate over time and compromise the headlight effectiveness. According to the recall notice, Audi will replace the xenon headlamp reflectors to solve this problem. This is, however, the only known 2002-2006 Audi A4 headlight problem.

Next is the 2004-2006 Audi A4 airbag recall, again connected to the ongoing Takata airbag saga, where the front passenger airbag's inflator could rupture during deployment. This could send metal fragments flying into the cabin and potentially cause serious injury. No other airbags are mentioned in this recall, though.

The last recall to note with the B6 Audi A4 concerns the coolant pump, but only applies to 1.8T engines that have had a Gates replacement coolant pump fitted. On the affected water pump, the drive pulley could fail, damaging the cambelt and causing internal engine damage due to the cam timing going out. Only 50 vehicles were affected, though, so your chances of running into one in the wild are extremely low.

On all 2002-2006 Audi A4 models, the following error codes may appear during an OBD-II scan:

  • P0010 indicates a problem with the variable valve timing actuator, and P1529 and P1531 show an electrical circuit problem in the valve timing actuator's wiring.
  • P0011 and P1340 indicate a problem in the phasing between the intake cam and the crankshaft, and P0340 and P0393 point toward a problem with the camshaft-position sensor's wiring. P0322 indicates a defective crankshaft-position sensor.
  • Error codes P0032 and P1120 relate to the oxygen sensor's heater circuit, P0139 is linked to a fault with the catalytic converter, and P0171, P1111, P1128, P1138, P1176, and P1177 say that the fuel mixture is leaner than optimal. Issues with the catalytic converter will be shown with error code P0420, when the catalyst efficiency drops below a predetermined value.
  • Getting P1142 on an OBD-II scan indicates a problem with the mass air-flow sensor (MAF) or its wiring, or may point to a vacuum leak.
  • P0118, P1290 and P1291 indicate a problem with the engine coolant temperature sensor, either due to faulty wiring or a defective sensor. P1296 means that there's a problem with the cooling system's hardware, such as insufficient water flow or a sticky thermostat.
  • P0229 and P1639 are unusual error codes, and relate to the accelerator pedal position sensor. P0638 indicates a problem with the electronically controlled throttle's actuator, P1171 means that there's a problem with the throttle position sensor itself, and P1222 indicates a defective throttle actuator motor. P1294 and P1559 are also linked to the throttle actuator and indicate that the target idle speed can not be reached.
  • A P0299 error code means that the turbo's boost pressure is too low. Check the PCV valve as a first step. A pressure drop between the turbo and the throttle valve will be indicated by P1297, in which case it's always a good idea to check the condition of the turbo diverter valve first. P0243 is connected to a wiring problem with the wastegate actuator solenoid.
  • A problem with the wiring to the knock sensors will present error code P0332, while P0333 relates to a problem with the knock sensor itself.
  • P0350 indicates a problem with an ignition coil malfunction due to a wiring problem, and substituting the last digit with any number from 1 to 6 will show which coil pack is experiencing trouble. For example, P0352 and P0356 indicate wiring problems on coil number two and coil number six.
  • P0411 and P1411 show a problem with the airflow through the secondary air injection system.
  • If the fuel system's evaporative purge valve is malfunctioning, you will encounter P0441, P0442, P0456and/or P1426.
  • Transmission errors will be identified by error codes P0706, P0730, P0745, P1624, and P1626, while P0741, P1741, P1743, P1751, P1753, P1770, and P1773 indicate defects in the torque converter clutch (or multi-plate clutches in the CVT)
  • P1479 indicates an error in the brake booster's vacuum system, typically caused by a vacuum leak in the hose which connects the booster to the intake manifold.
  • If there's an issue with the immobilizer which keeps the engine from starting, P1570 will show up on the OBD-II scan, and P1602 shows that the ECU supply voltage is too low. Only trust these error codes if the car's battery is in good condition, as low battery voltage could also trigger them. Battery voltage being too low will also trigger the P1794 error code.
  • P1649 and P1850 error codes indicate a communication interruption between the ECU and the rest of the Audi A4's data network. P1848 will be triggered when there's a fault stored in the ECU which affects other electronic systems.
  • The engine cooling fan control module could be problematic in B6 Audi A4s, and could lead to the P1931 error code being logged.
  • A malfunctioning coolant outlet temperature sensor (located on the lower radiator hose on the driver's side) will give the P1990 error code in a 2002-2006 Audi A4.

Audi A4 B6 Common Problems

Oil Sludge Formation

This is the leading cause of 2002-2006 Audi A4 engine problems, albeit mostly with the 1.8T engine, specifically because the turbo overheats the original (mineral) oil, which is why full-synthetic oil has since become recommended for these engines. There are reports of 3.0s suffering from this problem as well, but it happens much less often here than with the 1.8T, likely due to the V6 engine's much larger oil capacity.

If the 5,000-mile oil and oil filter replacements are not followed very accurately, the engine oil can decompose and form a layer of grease-like gunk in the engine sump. Over time, this sludge builds up to the point where it blocks the oil pump pick-up, leading to a loss of oil pressure and subsequent engine failure. 2002-2006 Audi A4 turbo problems are an indicator that something is amiss with the oil pressure, and could be the first failure point if there is any loss in oil pressure.

This issue is often misdiagnosed as a defective oil pump, but removing the sump to get to the oil pump almost always shows a thick layer of sludge instead. The best way to prevent sludge build-up is to keep the full-synthetic oil renewed every 5,000 miles, and just to be safe, removing the sump every 60,000 miles and cleaning out any accumulated sludge. Also clean and unclog the oil pump pick-up at the same time, and your A4 should be good to run for many more miles.

Mileage: From 40,000 miles on poorly maintained cars, but more than 60,000 miles on cars with a complete, synthetic oil service history.

Cost: Less than $100 to replace the oil and filter, but about three hours of labor plus fresh oil to perform a sump-off cleaning operation.

How to spot: Prolonged valve-lifter noise upon startup, oil-pressure warning light at idle, complete engine failure.

Cambelt and Coolant Pump Failure

This isn't necessarily a defect or a design flaw, but it bears mentioning that cambelt failure is also a major cause of serious engine damage in Audi A4s. On both these engines, the camshaft drive belt also powers the coolant pump, and, because the coolant pump could get problematic from around 60,000 miles, it is recommended that the water pump be replaced around that mileage.

While Audi says that the cambelt itself should be good for 105,000 miles, history has shown that this recommendation is rather optimistic. On top of this, there are also some 2002-2006 Audi A4 tensioner problems to consider, which may occur before 100,000 miles. Rather replace the cambelt, the cambelt tensioner, and the coolant pump every 60,000 miles instead, to ensure that these critical components continue to function as needed. Combine this operation with the sump service to cut labor charges slightly.

Mileage: Coolant pumps should be good for 60,000 miles, so replace the whole lot at that mileage to be safe.

Cost: About $69 for an OEM cambelt, $185 for the OEM cambelt tensioner, and $121 for the OEM coolant pump. Count on at least three hours of labor, depending on the workshop's experience with these engines.

How to spot: You might hear the water pump squeaking, or there may be visible coolant loss, but these components usually go bad without prior notice. Just replace them all regularly to avoid any issues.

Multitronic CVT Problems

Over the years, this CVT has earned a reputation for being rather fragile, especially so in cars equipped with the first-generation Multitronic, such as the Audi A4 B6. Even in cars where a 30,000-mile CVT fluid change regimen has been followed, aggressive driving or plain old age could lead to premature failure of this transmission. 2002-2006 Audi A4 CVT problems could be caused by ECU malfunctions, solenoids failing, or the seal between the differential and the CVT leaking through, causing excess slippage in the CVT and eventually wearing out the whole assembly.

Mileage: Multitronic failure could happen even before 60,000 miles, especially if not serviced every 30,000 miles.

Cost: Replacement CVT solenoids vary in cost between $350 and $800, a rebuilt Multitronic transmission could cost up to $3,500, and a new replacement gearbox will cost at least $7,500 from Audi.

How to spot: Sluggish acceleration, shuddering while accelerating or changing ratios, vibrations upon pull away, and eventually complete loss of drive to the front wheels.

Control Arm Failure

Starting with the B5-generation A4, Audi has been employing a clever multi-link front suspension system, which carried over to the B6 generation. These control arms are made from aluminum and have rubber bushings at their ends, which makes them more susceptible to damage over rough roads and general wear and tear. This also applies to the strut top mounts and suspension subframe bushes because they're also exposed to the same conditions.

Mileage: Control-arm bushes have failed from around 30,000 miles, depending on the usage conditions.

Cost: Depending on the bush in question, anywhere from $27 to $88 per bush, plus about three hours of labor to install a set of bushes.

How to spot: Knocking noises from the front suspension over uneven road surfaces, vague steering, and poor directional stability.

Ignition Coil Failure

Many cars with coil-on-plug ignition suffer from coil failure at some point, but this issue is more common on the Audi A4 B6 than most. This leads to 2002-2006 Audi A4 misfire problems, and while there is no definite reason for this, the problem is severe enough for Audi of America to have replaced coils on various 2001-2002 1.8T-equipped cars. This was not officially called a recall, and there was no 2003-2006 Audi A4 coil pack recall, either. But, even with the replaced (and uprated) coils, failure could still appear at any time. 3.0 models have also shown this issue, but it seems to be a far less common issue with the larger engine.

Mileage: Any time from 30,000 miles.

Cost: The upgraded OEM coils for an A4 1.8T cost about $17 each, but the 3.0's coils cost about $44 apiece. It's easy to fit them yourself, so there's no need to budget for labor.

How to spot: Misfiring, hard starting, irregular idle, reduced performance, rough running. Error code P0300 to P0306 will show up in an OBD-II scan, with P0300 indicating random or multiple misfires, and P0301-P0306 indicating the guilty cylinder(s) with the last digit.

Cooling System Leaks

Some of the cooling system components are made of plastic or sealed with rubber gaskets, and are prone to failure after enough heat cycles and due to engine vibrations. Most prevalent is the coolant outlet at the rear of the 1.8T's cylinder head, and the temperature sender unit's O-ring seal on both engines. Access to the various components can be tricky, especially with the 1.8T's rear outlet, but repairs can be done without any special tools except patience.

Mileage: From 70,000 miles or five years.

Cost: The 1.8T's coolant outlet flange costs only $37, and the sealing O-ring costs only about $2, both from Audi.

How to spot: Persistent coolant loss from the engine, traces of escaped coolant near water pipes, and puddles of coolant under the vehicle.

Window Regulator Failure

2002-2006 Audi A4 front- and rear window problems appear to be a common complaint and is often due to the regulator cables fraying, or a plastic clip inside the door breaking due to old age. In some cases, the window would simply be unresponsive, but in many cases, the window pane could drop into the door and refuse to come up again.

Mileage: Window regulators can start acting up at any time, but most owners only report this problem after 100,000 miles.

Cost: OEM window regulator assemblies cost from $166, but plastic window locator clips can be found in the aftermarket from a dollar or so. Labor could be anything from an hour to four hours, depending on the nature of the failure.

Less Common Problems And Problem-Free Areas

Brake-light switch failures are known to appear on many Audi products of this era, thanks to the dual-circuit switch employed at the brake pedal. The one circuit controls the actual brake lights, and the other signals to the engine's electronic control unit (ECU) when the brakes are activated. Problems usually arise with the latter circuit, which will prompt the ECU to partly close the drive-by-wire throttle and thus lead to many of the 2002-2006 Audi A4s' acceleration or traction-control problems. There will be an illuminated warning light on the dash if this happens, and could be diagnosed as a 2002-2006 Audi A4 EPC problem.

2002-2006 Audi A4 overheating problems could occur, but are usually due to a thermostat failure, the engine cooling fan not working properly, or a leaking overflow tank cap. 2002-2006 Audi A4 thermostat problems are fairly inexpensive and easy enough to fix, fortunately, and the component isn't difficult to access.

2002-2006 Audi A4 PCV valve problems are quite common. This item is made of plastic and degenerates over time. If the PCV valve malfunctions, it will introduce oil into the intake manifold, increasing oil consumption, and create a boost leak on the 1.8T engine.

Apart from the Multitronic problems described above, the five-speed automatic gearbox (Tiptronic) is responsible for some 2002-2006 Audi A4 automatic transmission problems, usually due to a lack of servicing or abuse. However, Audi A4 Tiptronic problems on the torque-converter transmissions usually don't appear if the car is correctly maintained. The five- and six-speed manual transmissions are quite robust, with few 2002-2006 Audi A4 manual gearbox problems to report.

Body-specific issues only really apply to the convertible top, where most 2003-2006 Audi A4 convertible roof problems are due to the hydraulic pump which powers the mechanism, position sensors that give incorrect signals, hydraulic leaks, or the rear window glass that may separate from the canvas top. Most of these issues are due to old age, but the system's complexity may make for an expensive repair. By the same token, 2002-2006 Audi A4 trunk-latch problems have been known to occur, and are usually caused by the original lubrication grease, which hardens when cold or with age.

There are no specific 2002-2006 Audi A4 sedan or Avant problems to report, and Audi A4 sunroof problems on this generation don't appear to be common among either sedan or Avant models, unlike some other old Audis that suffered endless sunroof leaks. The electrical system is quite robust, apart from occasional starter-switch failure, which is endemic to most Audis of this era. 2002-2006 Audi A4 starter/starting problems could also be due to a worn starter solenoid, but this generally only happens well past the 100,000-mile mark.

Some owners also note 2002-2006 Audi A4 radio antenna problems, which usually relate to the antenna's design or to the built-in signal amplifier. These hassles can usually be fixed quickly and inexpensively with a simple DIY operation behind the rear roof lining, or the receiver unit could be replaced at a cost of more than $300. 2002-2006 Audi A4 fuel gauge problems aren't common at all, and usually result from a defective fuel level sender unit.

Which One To Avoid

The least desirable B6 Audi A4 is anything with a Multitronic CVT, because it's fragile, unpleasant to operate, and will likely cost a fortune to keep running in the long term. It's particularly ill-suited to the 1.8T engine, where the CVT presents significant take-off lag, and this problem will be even more pronounced in the heavier cabriolet body. It follows that the B6 to avoid has to be any 2002-2006 Audi A4 1.8T Multitronic.

Which One To Buy

Many buyers prefer the secure handling which comes with quattro AWD, and the most practical car in the A4 range is the Avant. Sticking with a manual gearbox will alleviate the 1.8T's initial power lag, so a 2005-2006 Audi A4 Avant 1.8T quattro with the six-speed manual gearbox will be the most sensible choice with this engine.

Alternatively, a 3.0 quattro sedan will do a convincing imitation of a performance saloon, again with the manual gearbox by preference. Or, if you just want to cruise and don't need to cater for more than one passenger, a quattro automatic cabriolet will give you a very agreeable balance between power, smoothness, and drop-top sensory indulgence.

2nd Gen Audi A4 (B6) Verdict

Attractive, safe, solidly made, and very well-engineered, there's a lot to like about the B6 Audi A4. Just be absolutely sure that all the preventative maintenance, as well as regular servicing, is up to date before you sign on the dotted line, because improperly maintained or neglected examples are sure to become a money pit in short order. Ideally, an Audi A4 B6 owner should also have access to some tools and some DIY skills, otherwise, they may just end up paying for their local Audi specialist's holiday home if something goes wrong.

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