P0016 on BMW: How to Diagnose & Fix

The BMW S55 twin-turbo inline-6 engine has a critical design vulnerability where the crank hub is secured only by a single bolt with friction material - no keyway or mechanical lock. Under high load conditions such as aggressive downshifts, hard acceleration, or increased boost from tuning, the crank hub can slip. When this occurs, camshaft timing is thrown off and can cause catastrophic engine damage.

The S55 crank hub is secured by a single bolt with friction material and no keyway. Under high load, the hub can slip on the crankshaft, throwing off valve timing and causing catastrophic engine damage costing $20,000+. This is considered mandatory preventive maintenance for any tuned F80 M3 and strongly recommended for stock cars that see spirited driving. The SSR Performance 4-pin double-keyed kit is the industry standard fix, which requires drilling the crankshaft to lock both timing and oil pump sprockets permanently.

The F25 X3 with the N20 engine shares the well-documented timing chain guide failure issue. Plastic guides wear prematurely and can break apart, causing catastrophic chain derailment and engine damage. This is the most critical known issue for N20-equipped X3 models.

The N20 turbocharged four-cylinder in E84 X1 models is prone to premature timing chain guide wear and failure. Plastic chain guides become brittle and can break, causing chain slack, jumped timing, and potential catastrophic engine damage. Most failures occur between 60,000-100,000 miles.

The F82 M4 S55 twin-turbo engine is prone to crank hub bolt loosening, the most well-known S55 failure mode. The factory stretch bolt can back out under repeated thermal cycling and high-RPM use, causing the crank timing to shift and potentially destroying the engine. This is the #1 preventative fix for any S55-equipped BMW.

The S55 engine in F82/F83 M4 (2015-2020) suffers from catastrophic crank hub failures identical to the M3. The crank hub (harmonic balancer) is press-fit onto the crankshaft and can slip under high load, especially on tuned cars or during track use. When the hub slips, timing is lost and valves contact pistons, destroying the engine. The OEM crank hub has inadequate interference fit for the engine's power output. Failures typically occur between 30,000-70,000 miles on tuned cars or after multiple track days. This is considered the #1 critical failure point on S55-powered BMWs.

The N20 four-cylinder engine in the 1 Series is prone to premature timing chain stretch and guide failure, particularly in models built before 2015. The plastic chain guides become brittle over time and can break apart, allowing chain slack that leads to jumped timing. This can cause catastrophic engine damage if the chain skips enough teeth.

The B48 engine in the X2 can develop timing chain tensioner issues, particularly in earlier production years. While improved over the N20, the hydraulic tensioner can lose pressure, allowing chain slack that leads to noise and potential timing issues. Most commonly seen after 50,000 miles.

The E70 and F15 xDrive50i use generation-specific N63 boost-control hardware. BMW's N63 training shows that the wastegate valves are moved by vacuum units through electropneumatic pressure converters; hoses, reservoir, vacuum pump, converters, actuator linkage, charge-air leaks, and the turbocharger/wastegate hardware can therefore create overlapping rattle or low-boost complaints. Rattle alone does not prove both turbochargers failed, and the previously listed P0011/P0012/P0014/P0016/P0017 are cam-timing faults rather than wastegate identifiers. The N63 Customer Care Package is not a Central Cooling Pump campaign and does not promise generic wastegate or turbo coverage.

Certain 2010-2013 E70 X5 xDrive50i vehicles with the early N63 engine were included in BMW's timing-chain wear-check procedure. VANOS or camshaft-position faults can distort the timing-chain test, so they must be diagnosed first. BMW then measures chain elongation with the applicable ISTA test plan; only a 'Timing chain is not OK' result establishes the chain-replacement path. Chain wear can affect valve timing and can lead to serious engine damage if an out-of-spec condition is ignored, but a rattle or generic timing code alone does not prove the chains or a single tensioner are the cause.

Certain model-year 2010-2013 E70 X5 vehicles with an N52-family or N55 inline-six engine are included in BMW/NHTSA safety recall 23V-707. Aluminum fasteners in the intake and exhaust VANOS adjustment units can loosen or break, causing incorrect camshaft adjustment, unusual engine noise, rough running, a check-engine warning, reduced-power mode, a no-start condition, or, rarely, an engine stall. These symptoms and VANOS/camshaft faults do not by themselves prove that replaceable control solenoid 11-36-7-585-425 has failed, and the recall does not apply to every X5 engine or model year.

The N20 2.0L turbocharged engine in 2015-2016 X4 xDrive28i models suffers from premature timing chain stretch and guide failure, typically between 40,000-80,000 miles. The single-row timing chain design is inadequate for the engine's power output. Chain stretch causes timing to jump, leading to rough running, poor performance, and potential catastrophic engine damage if the chain breaks. BMW issued a class action settlement covering 8 years/100,000 miles. This is identical to the N20 issue affecting all N20-powered BMW models including X3, 3/4 Series, and X1.

The N63TU3 4.4L twin-turbo V8 in M850i models uses plastic timing chain guides that wear prematurely under the extreme heat and stress of the hot-V configuration. As the plastic guides wear, the timing chain develops slack, causing rattling on cold starts and eventually risking timing chain skip or failure. Chain skip causes piston-to-valve collision and catastrophic engine destruction ($15,000-$25,000 replacement). While the N63TU3 has improved guides over earlier N63 versions, the fundamental plastic guide material still degrades from heat cycling. Turner Motorsport offers a complete timing chain guide kit (11317594899KT) with all necessary components. Bimmerpost consensus: replace timing chain guides preventively at 80,000-100,000 miles on N63TU3 engines before catastrophic failure.

The BMW B38 1.5L 3-cylinder turbocharged engine in the i8 develops turbocharger and timing chain issues at higher mileages (70,000+ miles). The turbocharger can develop oil leaks from the turbo oil feed/return lines and bearing seal degradation. Carbon buildup on intake valves is significant due to direct injection, requiring walnut blasting every 40,000-60,000 miles. The timing chain is marketed as "lifetime" but reports of chain stretch and noisy timing components increase on higher-mileage examples, especially those driven with extended oil change intervals. The B38 in the i8 operates differently than in a Mini or 1 Series due to the hybrid system - the engine doesn't run continuously, which can cause condensation and oil dilution from short run cycles.

The N63 twin-turbo V8 places the turbos inside the vee, and the trapped heat cooks the plastic timing chain guides until they crack and break apart. Debris from a shattered guide lets the chain go slack, so it stretches, throws timing correlation codes, and can jump a tooth - at which point one whole bank stops firing and the driver gets a Drive Train Malfunction with reduced power. Owners on the F01 chassis have reported broken guides and a jumped chain around 100,000-120,000 miles, often preceded for months by a rattle or grinding noise during the first few seconds after a cold start. Early N63 engines (roughly 2009-2013) were the worst and were covered in part by the Customer Care Package rework.

The 1.5-litre three-cylinder B38 petrol engine (216i/218i) can suffer timing-chain elongation. The higher per-cylinder load on a three-pot stresses the chain, and worn chain tensioners lose the ability to keep correct tension. The classic symptom is a metallic rattle for a few seconds on cold start, typically appearing around 80,000-120,000 km, accompanied by rough running and power loss. Neglected oil changes and extreme short-trip driving accelerate the wear. If the stretched chain jumps a tooth the pistons can contact the valves, causing major engine damage. Early B38 manual cars (pre-April 2015) also had isolated crankshaft axial-bearing failures.

BMW SIB 11 03 17 identifies F10 528i and 528i xDrive sedans with the N20 engine produced from September 1, 2011 through February 28, 2015. The bulletin covers defects in the timing-chain and oil-pump drive-chain modules; it does not say every 528i is defective or prescribe mileage-based preventive replacement.

BMW SIB 11 16 14 applies to F10 5 Series sedans with the N63 engine produced from March 2010 through July 2013. It defines an ISTA timing-chain elongation test intended to detect wear and provide a repair path; BMW states that this N63 timing-chain check and Customer Care Package are not recalls or mandatory technical campaigns.

Aging E39 M5 engines can suffer from brittle timing chain guides and weakening chain tension components, especially at higher mileage. Owners report startup chain slap, persistent front-engine rattling, and concern over guide fragmentation contaminating the oil system. While not every S62 fails this way, it is a documented high-cost issue in the E39 M5 community because neglected guide wear can lead to timing errors and severe engine damage.

The M2 Competition shares the S55 engine with M3/M4 and inherits the catastrophic crank hub failure issue. The crank hub (harmonic balancer) is press-fit onto the crankshaft and can slip under high load, especially with upgraded software or track use. When the hub slips, timing is lost and valves contact pistons, destroying the engine. This is the same critical failure point as the F80 M3 and F82 M4. The OEM crank hub has inadequate interference fit. Most failures occur on tuned cars or during hard track use between 30,000-70,000 miles.

The N20 2.0L turbocharged engine in 428i models suffers from premature timing chain stretch and guide failure, typically occurring between 40,000-80,000 miles. The single-row timing chain design is inadequate for the engine's power output. Chain stretch causes the timing to jump, leading to rough running, poor performance, and potential catastrophic engine damage if the chain breaks. BMW issued a class action settlement covering 8 years/100,000 miles. This is identical to the N20 timing chain issue in 328i/X3/X5 models using the same engine.

BMW SIB 11 03 17 identifies specified F30, F31 and F34 3 Series variants with N20 or N26 engines produced through February 2015. A whining noise from the lower engine area that rises with engine speed can be associated with wear in the timing-chain or oil-pump drive-chain system; the bulletin does not declare every 2012-2015 3 Series defective.

BMW SIB 11 16 14 includes F12 6 Series convertibles with the N63 engine produced from March 2011 through July 2012 and F13 6 Series coupes with the N63 engine produced from July 2011 through July 2012. It defines an ISTA timing-chain elongation test; BMW states that the check and related Customer Care Package are not recalls or mandatory technical campaigns.

The N63 4.4L twin-turbo V8 engine in E71 (2008-2014) and F16 (2015-2018) X6 xDrive50i models suffers from premature timing chain stretch and guide failure. This is the same catastrophic issue affecting X5 xDrive50i. The plastic timing chain guides disintegrate from the extreme heat generated by the "hot-vee" turbocharger configuration where turbos sit between the cylinder banks. Timing chains stretch, guides crack and break, leading to chain jump or failure causing piston-to-valve collision and complete engine destruction ($15,000-25,000 replacement). BMW issued TSB B001314 in 2014 acknowledging the issue. Bimmerpost consensus: avoid 2008-2014 N63 models unless timing chain has been replaced with updated parts.