2015 Infiniti Q70 2.1L Diesel · DW55 SDW

The Mercedes-sourced 2.1-litre (badged 2.2d) OM651 four-cylinder turbodiesel engine fitted to post-2015 Q70 models features a timing chain mechanism mounted at the rear of the engine block near the bulkhead. Over time, the hydraulic timing chain tensioner can bleed down or lose tension, causing the single-row chain to stretch. On cold startup, this causes a distinct metallic clattering sound. If left unaddressed, the stretched chain can skip teeth on the camshaft sprockets or snap entirely, leading to catastrophic valve-to-piston contact and engine destruction. Replacing the rear-mounted timing chain assembly requires gearbox removal or engine extraction, incurring significant workshop labour.

On M35h and Q70 Hybrid models, the high-voltage hybrid powertrain relies on an auxiliary 12V battery in the boot to energise the hybrid system relays and boot the computer modules. The vehicle suffers from parasitic electrical draw when parked for extended periods (seven to ten days), draining the 12V battery and preventing the car from entering 'Ready' drive mode. Furthermore, high-mileage hybrid models can experience internal contact wear within the high-voltage DC-DC inverter relay assembly or cooling circuit airlocks in the inverter cooling loop, triggering hybrid system warning messages and disabling pure-electric EV gliding mode.

High-specification S, S Premium, and Sport Tech versions of the M and Q70 were fitted with Infiniti's 4-Wheel Active Steer (4WAS) system, which uses an electronically controlled electric motor and mechanical actuator rack on the rear axle to turn the rear wheels up to one degree. Exposed to UK road spray and winter road salt, the rear steering actuator housing and wiring connectors suffer from corrosion, water ingress, or internal sensor failure. When the actuator faults, the rear wheels can lock in an off-centre position, causing the car to pull or feel nervous on the motorway and triggering an amber 4WAS warning light on the instrument binnacle.