2002 Audi A8 Problems: 6 Known Issues

On the 1997-2003 Audi A8, the D2 A8 4.2L V8 (both the early 32-valve ABZ and the later 40-valve AUX/AWN/AKB) is an interference engine driven by a rubber timing belt. The original published interval was 105K miles on the C5 and D2 4.2, until Audi retroactively changed it to 75,000 miles. Many original-owner cars went well past 100k on the factory belt, and high-mileage examples are commonly bought with no timing belt service history. By the 75,000-mile service, age has put the tensioner(s), damper, water pump, and other seals and O-rings at or near the end of their service life. Owners who replace only the timing belt can see it fail 10,000-20,000 miles later from a tensioner, idler bearing, or water pump failure. Belt or tensioner failure on this engine bends valves and is typically a total-loss event for an older A8.

On the 1997-2003 Audi A8, the Bosch 5.3 ABS/EBCM control module mounted to the side of the hydraulic pump unit suffers from internal solder joint and fine aluminum bond-wire fatigue, causing intermittent then permanent loss of ABS function. The Audi ABS pump & module system has been a very common failure for a long time, and the problem usually starts with the ABS light coming on intermittently but after a while becomes constant. Failed Bosch 5.3 control modules are extremely common in 2000-era Audis. On D2 A8/S8 cars, drivers typically see simultaneous ABS and red brake warning lights with three beeps at startup, and communication with the controller can drop out entirely (Link Error in VAG-COM). The ABS 5.3 system was introduced mid-1997 on the D2 platform; note that the 2002+ S8 reverted to a 5.0-based system, so verify the module on the car before ordering a repair.

On the 1997-2003 Audi A8, the D2 A8's hydraulic system uses Pentosin mineral oil shared between the power steering pump, ZF rack with Servotronic module, and (on non-NA self-leveling cars) the rear shock accumulators. Owners report leaks in the middle of the pump where the two-piece housing is bolted together, often diagnosed with UV dye. Whining on cold start, low fluid in the trunk-mounted reservoir, and visible Pentosin (green) under the engine are classic signs.

On the 1997-2003 Audi A8, the 4.2 V8 in the D2 A8 (both the early 32-valve ABZ and the later 40-valve AKB/AUX/AYS) runs a vacuum-operated secondary air injection system with one combi valve per cylinder head, fed by small-diameter hard plastic vacuum lines that become brittle with heat and crack. Both banks have their own combi valve, and it is usually the hard vacuum line that goes to them that breaks and causes a vacuum leak and inoperable SAI. Owners report replacing vacuum hoses and the SAI relay only to have the check-engine light return, then moving on to the SAI pump, the solenoid on top of the engine and the combi valves aft of each cylinder head, along with cleaning carbon buildup from the cylinder head ports. The main symptom is a check-engine light shortly after a cold start with P0410 (or banked variants P0491/P0492).

On the 1994-2002 Audi A8, factory-fitted options included halogen, D2S/H7 single-xenon, and D2R/H7 single-xenon headlights manufactured by Bosch (Automotive Lighting); the halogen H7 reflectors lose their reflective layer as it peels off from bulb heat and ageing, and the single-xenon 2.5-inch projectors are known to lose their reflective layer until they go black inside, causing dangerously low light output. On the 'Xenon Plus' headlights, a plastic diffuser sits right in front of the xenon lamp; heat and light intensity yellow the diffuser and cause micro-cracks that scatter the beam, and this diffuser is not a replaceable part and nothing can restore it. Drivers notice progressively dim night-time lighting and a cloudy/milky appearance to the projector lens.

On the 1994-2002 Audi A8, the D2 A8 uses a VDO-built instrument cluster with a central LCD for the odometer, trip computer, gear indicator and clock. As these clusters age, the display loses pixels. Whole horizontal or vertical lines can go missing, the screen can fade or lose contrast, and on some cars more pixels drop out once the cluster warms up. Cluster repair specialists list the A8 next to the B5 A4, which uses a related VDO cluster, as prone to this LCD pixel failure. Parts suppliers blame the joint where the silver ribbon cable is heat-bonded to the LCD. This connection loosens over time, so some segments stop getting a signal. When that happens you can no longer read the mileage or trip information.