The Q50 was Infiniti's European challenger to the BMW 3 Series and Mercedes-Benz C-Class. Powered by the Mercedes-Benz OM651 diesel engine and built on a rear-wheel-drive platform, it offered generous standard equipment and a distinctive design at a lower price than its German rivals. The 2.2d was produced from 2014 to 2018, with leftover stock still being sold into early 2019. Infiniti ended new-car sales in Western Europe on 31 March 2020. An authorised maintenance network still handles servicing, repairs, warranty work and genuine parts, but geographic coverage is far thinner than before, so parts sourcing and specialist knowledge require more effort than with mainstream premium brands.· more· less
Mercedes OM651 engine, parts widely sourcedStrong equipment levels for the price
No new-car sales network in Europe since 2020, thin service coverageSteer-by-wire system reliability concerns
Buy if: You want a well-equipped rear-drive diesel saloon at a steep discount and have access to a Mercedes-experienced independent workshop.
Avoid if: You need an authorised workshop close to home or are not prepared to source Infiniti-specific body and electrical parts from international suppliers.
Plastic chain guides degrade and chain stretches, typically from 120,000 km onward · more· less
The OM651 uses a simplex timing chain at the rear of the engine with plastic guides that deteriorate with heat and age. As guides crumble and the chain elongates, a distinctive rattling noise appears during cold starts and eventually under acceleration. The timing chain on the OM651 is located at the transmission side (rear of engine), making replacement labor-intensive. Independent specialist replacement typically costs €1,400-1,800, while dealer-level work can reach €2,500. If the chain snaps or jumps, pistons contact valves and the engine is usually destroyed. Regular oil changes with the correct ACEA C3 specification oil significantly extend chain life. Many OM651 engines reach 200,000+ km without issue when well maintained, but the risk increases substantially beyond 120,000 km.
Direct Adaptive Steering (DAS) ECU failure
€1,500 - 3,0002 of 7
Optional steer-by-wire system can lose responsiveness or alter turning radius without warning · more· less
The Q50 was the first production car offered with a fully electronic steer-by-wire system, sold as the optional Direct Adaptive Steering, so this risk applies only to cars actually equipped with it. On early cars the DAS is known for intermittent loss of feedback, sudden stiffness changes, and steering that feels disconnected. A European recall covered a software calibration update for DAS-equipped cars built between 13 December 2012 and 18 December 2015, but the underlying ECU can still fail. Symptoms include vague steering feel, warning lights, and in rare cases a temporary reversion to the mechanical backup column. ECU replacement costs €1,500-3,000 depending on whether new or refurbished units are sourced. Post-2016 facelift models received improved DAS software and hardware, reducing the failure rate significantly. If equipped with conventional hydraulic steering (offered on some European base models), this issue does not apply.
Injector seal leak (black death)
€300 - 1,5003 of 7
Copper sealing washers under injectors degrade, allowing combustion gases to escape and carbonize · more· less
This is a well-documented OM651 issue. The copper sealing washers beneath the fuel injectors degrade from heat and pressure cycling. Once the seal fails, hot exhaust gases leak past and create hard black carbon deposits around the injector wells. If caught early, new copper washers cost under €20 each and a specialist can clean and reseal for €300-500 total. If ignored, the carbon buildup can seize injectors in place, requiring extraction with specialist tooling and potentially damaging the cylinder head. Advanced cases with stuck injectors and head cleaning can reach €1,500. Most technicians report seeing early signs between 100,000 and 160,000 km. Annual inspection of the injector area is recommended.
DPF clogging and regeneration failure
€300 - 2,5004 of 7
Diesel particulate filter blocks from short-trip driving when exhaust temperatures stay too low for regeneration · more· less
The OM651 relies on both passive and active DPF regeneration. Passive regeneration occurs naturally during sustained highway driving at sufficient exhaust temperature, while active regeneration is triggered by the ECU when soot loading exceeds 40-50%, injecting extra fuel to heat the exhaust to approximately 600 degrees Celsius. Cars used predominantly for short urban trips never reach these temperatures, causing progressive soot accumulation. A forced regeneration at a workshop costs €200-400. Chemical DPF cleaning costs €300-500. Full DPF replacement can reach €1,500-2,500 including labor. Weekly highway driving of 20+ minutes significantly reduces this risk. The DPF pressure differential sensor (fault codes P244A) can also fail independently, costing €200-400 to replace.
EGR cooler internal leak
€800 - 1,4005 of 7
Internal passages crack from thermal cycling, allowing coolant to enter the exhaust system · more· less
The OM651 EGR cooler is prone to internal cracks from repeated heating and cooling cycles. When the cooler leaks, engine coolant enters the exhaust stream, producing white smoke and accelerating DPF contamination. Symptoms include unexplained coolant loss without visible external leaks, white exhaust smoke, and poor heater performance. Short-trip driving with frequent cold-warm cycles accelerates the failure. Replacement costs €800-1,400 including labor at an independent specialist. The issue is particularly common on pre-2015 OM651 engines, but later production units used in the Q50 are not immune. Checking coolant level regularly is the simplest early warning.
NOx sensor and AdBlue system failure
€400 - 1,0006 of 7
NOx sensors drift out of calibration or the AdBlue dosing module fails, triggering engine management warnings · more· less
The OM651 in Euro 6 specification uses selective catalytic reduction (SCR) with AdBlue injection. The system relies on upstream and downstream NOx sensors to monitor emissions performance. Sensor drift, connector corrosion, or wiring damage can trigger persistent warning lights and potentially a countdown to engine power restriction. A single NOx sensor replacement costs €300-600 for the part plus €100-200 labor. The AdBlue dosing module or heater can also fail, particularly if poor-quality AdBlue has been used, adding €300-500 to the repair. Total system repair in worst cases reaches €1,000. These are the same components used across Mercedes-Benz C-Class and E-Class models, so parts are readily available.
Mass airflow sensor malfunction (P0101)
€200 - 4007 of 7
MAF sensor triggers fault code P0101, often after air filter replacement without ECU adaptation reset · more· less
The Q50 2.2d is known for recurrent P0101 fault codes related to the mass airflow sensor. A common trigger is replacing the air filter with a non-original part without performing the ECU adaptation reset via a diagnostic tool, as the engine management interprets the changed airflow characteristics as a sensor fault. Symptoms include rough idle, reduced power, and check engine light. A genuine MAF sensor costs €150-250, with labor around €50-100. Before replacing the sensor, a specialist should attempt an adaptation reset using Mercedes-compatible diagnostic software (the Infiniti-specific tool is increasingly rare in Europe). Using OEM-specification air filters and performing the adaptation reset after each filter change prevents most occurrences.
Mercedes engine is proven, but orphan-brand status adds complexity
The OM651 diesel engine is one of Mercedes-Benz's most widely produced units, used across the C-Class, E-Class, and Sprinter range. Engine parts are readily available and well understood by independent Mercedes specialists across Europe. Infiniti-specific components like the Direct Adaptive Steering system, body panels, interior trim, and electrical modules take more effort to source since Infiniti stopped selling new cars in Europe on 31 March 2020. Its authorised maintenance network still supplies genuine parts and carries out servicing, repairs and warranty work, but there are far fewer sites and some countries have none. A Mercedes-experienced workshop can handle all engine-related maintenance and repairs, but steering, suspension, and body work may require parts from an authorised Infiniti outlet, an international dealer or a specialist breaker. Owners who accept these constraints and maintain the OM651 with regular oil changes and sustained highway driving report dependable long-term ownership.
Service history
Complete records from any workshop essential. Verify oil changes every 12 months or 15,000 km with ACEA C3 specification oil.
Tires
Check tread depth, tire age (date codes), and uneven wear patterns. Rear tires wear faster on this rear-wheel-drive platform.
Cold start
Engine must be started completely cold. Listen carefully for any rattling or metallic noise in the first 30 seconds.
Test drive
Minimum 30 minutes including highway driving. Pay close attention to steering feel and any warning lights.
Specific for this vehicle
Listen for timing chain rattle on cold start
A distinctive metallic rattling from the rear of the engine during the first 10-30 seconds of a cold start indicates timing chain or tensioner wear. This is the most critical check for the OM651 engine.
Test Direct Adaptive Steering response
During the test drive, check for any delay, vagueness, or inconsistency in steering response. Try low-speed parking maneuvers and higher-speed lane changes. Watch for any steering-related warning lights on the dashboard.
Inspect injector area for carbon deposits
Look around the fuel injector wells on top of the engine for any black crusty carbon buildup. This indicates leaking injector seals (black death) and requires immediate attention.
+ 4 more checksShow less
Check DPF health and driving pattern history
Ask about the car's typical use. Short-trip city driving accelerates DPF clogging. During the test drive, watch for DPF warning lights or excessive exhaust smoke.
Verify coolant level and condition
Low coolant without visible external leaks suggests an internal EGR cooler leak. Check for any white residue around the EGR area and any sweet smell from the exhaust.
Confirm all recalls have been completed
Have an authorised Infiniti or Nissan dealer run a VIN check. The DAS steering software recall applies only to cars fitted with the optional Direct Adaptive Steering built between 13 December 2012 and 18 December 2015. The driveshaft campaign R24A5/R24A7 is VIN-specific and can reach any Q50 V37 built up to 19 May 2022. UK recall R/2015/027 (R1503) covers diesel VINs with the JN1BDAV37 prefix built between 15 April and 22 December 2014.
Check brake pad thickness carefully
The Q50 has a known issue with accelerated brake pad wear due to thin brake pins and ABS cornering intervention. Check remaining pad thickness on all four corners.
Recalls and Technical Service Bulletins
Direct Adaptive Steering ECU software update, only on cars fitted with the optional Direct Adaptive Steering, European build window 13 December 2012 to 18 December 2015Verify if applicable
Driveshaft fatigue and potential breakage, European campaign R24A5/R24A7, VIN-specific and covering affected Q50 V37 production from start of production to 19 May 2022, VIN check requiredCritical - verify completed
UK recall R/2015/027 (R1503), timing chain tensioner gasket oil leak that can cause the engine to stall, Q50 VINs with the JN1BDAV37 diesel prefix built 15 April to 22 December 2014Critical - verify completed
Contact an authorised Infiniti or Nissan dealer with the VIN to verify all recalls have been completed. Infiniti no longer sells new cars in Western Europe, but its authorised maintenance network and Nissan dealers can access the recall database. The driveshaft campaign R24A5/R24A7 is VIN-specific rather than year-based and can reach cars built up to 19 May 2022, so only a VIN check shows whether a given Q50 is affected. It matters, because a broken driveshaft causes complete loss of drive power. UK recall R/2015/027 (R1503) is the one written specifically for this diesel: on VINs with the JN1BDAV37 prefix built between 15 April and 22 December 2014, a leaking timing chain tensioner gasket can let oil escape and stall the engine.
Warranty Status
Factory warranty (3 years / 100,000 km)Expired on all Q50 models
Infiniti European new-car salesEnded 31 March 2020, authorised service network retained
Authorised service and Nissan dealer supportServicing, repairs and parts available, coverage varies by country
All Q50 2.2d models are well outside their original factory warranty. Infiniti ended new-car sales in Europe on 31 March 2020, but an authorised maintenance network still provides servicing, repairs, warranty support and genuine parts. What disappeared is the sales network and the density of the service network, so the nearest authorised site can be a long drive away and some countries have none at all. Some Nissan dealers also handle basic servicing and recall work. For the OM651 engine, any Mercedes-Benz independent specialist can perform all maintenance and repairs using standard Mercedes parts.
Sources: Research draws on model-specific owner forums and owner communities, recall information from official authorities, German automotive press, and multiple workshop cost references cross-checked against each other.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.
