The balance shaft module drives the oil pump through a hexagonal shaft stub. That hex and its mating part gradually round off, until the shaft finally turns freely: the oil pump stops and the oil pressure is gone. The process gives no warning, and that is exactly what makes it dangerous. The failure typically happens at high revs, and the oil pressure light comes on only once the damage is already done. The factory hex is undersized, so it knocks against the wall of the bore, and the wear accelerates itself. The maker classed it as a "tolerance deviation" and, given the small number of cases against total production, did not recommend preventive repair; Audi alone ran a service action (13D7). The replacement is expensive: on the German market the module replacement is 1,300 to 1,700 euro, and an independent repair touching only the hex is around 650 euro. The reported cases cluster around the Passat B6, Sharan, Audi A4/A6, Superb and Alhambra, in model years between 2005 and 2009. This layout is not only on the pump-injector (PD) engines, it is on the common rail EA189 engines too: the same module, the same hex, the same wear. The failure is typically reported between 100,000 and 160,000 km. The first sign is a short flash of the oil pressure light, in a long bend or a few seconds after a cold start, and then quiet again. The versions without balance shafts (BKD, BMM, BMN, AZV) drive the oil pump differently and are not affected by this wear. If the light stays on or flashes, stop as soon as it is safe, switch the engine off, and do not restart it until the oil pressure has been measured.

On these engines the oil pump is driven by its own small toothed belt, and that belt runs in the hot engine oil. This is not the large timing belt that drives the camshafts, it is a separate belt in the lower part of the engine. In the oil the rubber hardens over time, its surface starts to crumble, and the loose particles block the suction side of the oil pump, so the oil pressure drops. If the belt snaps, the oil pump stops at once and the engine is left without lubrication within seconds. The rubber crumbs can also ruin the turbocharger and the camshaft adjuster, because they are lubricated from the same oil circuit. The maker specifies no replacement interval for this belt, so most cars still carry the one fitted at the factory, and the failures are reported above 150,000 km. Oil outside the specification and a stretched oil change speed the process up, because this belt ages in the oil. Replacing the belt itself costs between 200 and 600 euro, as long as the engine has not run without oil pressure.

The EGR valve and its cooler block up with soot and oily deposits; the particulate filter cannot regenerate on short urban trips. The signs are reduced power, a warning light, and frequent regeneration. The software update after the diesel emissions affair made the EGR operate more often, which accelerated the phenomenon: the maker gave goodwill repairs in several cases.

The internal springs of the flywheel tire, and the two discs knock against each other. The signs are a rattling or knocking from the bellhousing at idle and when releasing the clutch pedal, and vibration through the floor. If the clutch slips without a burnt smell, that also points to the flywheel. It is worth replacing in time: a disintegrated flywheel can destroy the bellhousing too. At a clutch replacement the two go together anyway.

The vanes of the variable geometry turbo are glued together by soot and oil arriving through the EGR. First you get overboost or a lack of boost, then loss of power above 2,000 rpm, and finally limp mode. Caught in time it is enough to remove the turbo, clean it and fit a new actuator rod. Short urban trips and gentle, low rev driving speed up the deposits.