P0017 on Audi: How to Diagnose & Fix

The Q5 2.0T uses the EA888 engine with the well-documented timing chain tensioner weakness. The 8R Q5 (2009-2017) is particularly affected as the heavier SUV puts more load on the engine. The tensioner loses pressure overnight, allowing chain slack on cold starts that progressively worsens until the chain jumps timing.

The A5 shares the B8/B8.5 platform with the A4 and inherits the same EA888 2.0T timing chain tensioner weakness. The original tensioner design allows the chain to slacken on cold starts, eventually jumping teeth and causing catastrophic valve-to-piston contact. Pre-2013 engines are most affected.

The B8/B8.5 A5 with the 2.0 TFSI engine (2008-2016) suffers from premature timing chain tensioner failure, identical to the A4 and A6. The tensioners wear out between 60,000-120,000 miles, causing the timing chain to stretch and rattle. A loud rattling noise on cold start from the front of the engine is the classic warning sign. If ignored, the timing chain can jump timing or break, causing catastrophic valve-to-piston contact and destroying the engine. Early B8 models (2008-2012) are more prone to failure than later B8.5 models (2013-2016). A5OC forum members report many failures under 100,000 miles, with some owners experiencing complete engine destruction. The repair requires removing the front of the engine and costs $2,000-$5,000. Some owners report oil consumption issues leading to accelerated tensioner wear.

The D3-generation S8 uses the 5.2L FSI V10 (shared lineage with the Lamborghini Gallardo/R8 V10). Its timing is driven by chains with plastic guides and hydraulic tensioners located at the rear of the engine. Over time and with deferred oil changes, the tensioners and guides wear, producing a rattle on cold startup that can persist. If a guide breaks or the chain skips, valve-to-piston contact can cause catastrophic engine damage. Access is poor (rear of the V10), making this an engine-out-level job and one of the most expensive risks on the D3 S8.

The Audi TTS Mk2 (2009-2015) with early EA888 engines (Gen 1 and Gen 2) suffers from timing chain tensioner failure, the same critical issue affecting A3, A4, and A5 models with this engine. The tensioner's ratchet mechanism wears, allowing the piston to retract when the engine is off. On restart, the slack chain can jump teeth on the camshaft sprockets, causing valve-to-piston contact and catastrophic engine destruction. The signature warning sign is a brief rattle (0.5-1 second) on cold or semi-warm startup as the tensioner takes up chain slack. The TTS's higher output tune puts more stress on the timing chain system, potentially accelerating wear. TTForum.co.uk documents numerous cases of complete engine destruction from ignored timing chain rattle. Early models (2009-2012) with the earlier tensioner revision are most at risk.

The B6/B7 S4's 4.2L V8 (BBK/BHF) drives its timing chains from the BACK of the engine, against the firewall. What owners call "timing chain failure" is really the plastic chain guides, the chain tensioners and the two camshaft adjusters wearing out and disintegrating. Forum documentation shows plastic guide fragments sitting on the chains, with cases reported at roughly 100k-112k miles. Because the chain drive is at the rear, there is no way in from the front of the car: the engine (or at minimum the whole drivetrain assembly on a subframe drop) must come out. This is the single defining failure of this generation and is NOT shared with the B5 2.7T (belt-driven) or the B8/B9 V6s. Left alone, a snapped guide lets the chain jump timing and destroys valves and pistons on an interference engine.

The 4.2L FSI V8 (BAR) in the first-generation Q7 4L uses a rear-mounted timing chain drive with plastic chain guides and hydraulic tensioners. The guides embrittle and the tensioners lose their ability to take up slack, especially on engines run past their oil-change interval or on short trips where sludge forms. Owners first hear a brief rattle at cold start that grows into a constant rattle or whine, and eventually the chain jumps a tooth and sets cam/crank correlation faults. Because the chain drive is at the back of the engine, the correct repair requires pulling the engine (or engine and transmission) out of the vehicle - which is why this failure so often totals an otherwise good high-mileage Q7.

Owners of three-cylinder 1.0 TFSI and four-cylinder 1.4 TFSI Q2s have reported the toothed cambelt snapping well before Audi's stated 5-year / ~75,000-mile replacement interval, in several documented cases between roughly 39,000 and 49,000 km/miles, with full service history. Because these are interference engines, a snapped belt causes the valves to collide with the pistons, leading to catastrophic internal damage and frequently an entire engine replacement. Contributing factors cited by owners and forum moderators include the extra start/stop cyclical loading on the belt and frequent short journeys, plus belt tensioner/bolt loosening. Audi typically offered only partial goodwill rather than full coverage out of warranty.

The C6 A6 with the 3.2L V6 and 4.2L V8 engines suffers from timing chain tensioner failures due to wear over time. Audi designates the chains and tensioners as "lifetime" parts requiring no maintenance, but they fail as early as 80,000-120,000 miles. The 3.2L engine has 4 chains, 3 tensioners, and several guides—all prone to wear. A loud rattling or clicking noise on cold start from the upper rear of the engine is the classic symptom of failing tensioners. If ignored, the timing chain can jump or break, causing catastrophic valve-to-piston contact and complete engine destruction. The transmission must be removed for full access, making this a labor-intensive repair. AudiWorld forums report low-mileage cars with stretched chains due to the design flaw.