IsItAGoodCar
Reliability Guide

Common Problems with the
2015 Infiniti Q70 (M)

A substantial facelift introduced the Q70 moniker, a Mercedes-sourced 2.2d diesel engine, updated double-arch grille styling, full LED headlights, and retuned dampers.

What changed for 2015

  • •Renamed from Infiniti M to Q70 with refreshed front and rear styling, revised LED headlamps, and new bumpers
  • •Introduction of the Euro 6 Mercedes-Benz OM651 2.2-litre four-cylinder turbodiesel engine producing 168bhp and 400Nm
  • •Discontinuation of the older 3.0d V9X V6 diesel to improve fleet running costs and CO2 emissions
  • •Re-engineered suspension bushings and retuned shock absorbers to enhance low-speed UK ride comfort

Common MOT watch-outs

  • !Emissions warning light illumination or high soot opacity on 2.2d diesel models from fouled DPF or EGR valves
  • !Play in front lower suspension control arm ball joints and worn anti-roll bar drop links over rough road surfaces
  • !Handbrake efficiency failure due to sticking electronic parking brake actuators on the rear calipers
3
Known Issues
2
Serious
1
Moderate
0
Minor

All Known Issues

OM651 2.2d Timing Chain Tensioner and Chain Stretch

SeriousEngine

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.

Est. Repair Cost: £900–£1,800
Warning Signs:

Loud metallic rattling or slapping noise from the rear of the engine on cold startup lasting more than three seconds, Check engine light illuminated with camshaft or crankshaft position correlation fault codes, Rough engine idle and hesitation under gentle acceleration when cold, Engine misfire or failure to start in advanced stages of chain elongation

What to Inspect:
  • Start the engine from stone cold and listen intently near the cabin bulkhead for any metallic clatter during the first 5 seconds
  • Check the service history for strict adherence to Mercedes MB 229.51 or 229.52 low-ash engine oil specifications and timely oil changes
  • Scan the engine control unit for stored diagnostic codes relating to camshaft and crankshaft timing correlation
Verified by IsItAGoodCar Research TeamUpdated

4-Wheel Active Steer (4WAS) Rear Actuator Failure

SeriousSteering

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.

Est. Repair Cost: £600–£1,600
Warning Signs:

Amber '4WAS' warning lamp continuously illuminated on the instrument cluster, Steering wheel sitting noticeably off-centre when driving straight on a level motorway, Unsettled or twitchy handling feel from the rear axle during high-speed lane changes, Diagnostic trouble codes relating to the rear steering angle sensor or actuator motor circuit

What to Inspect:
  • Scan the 4WAS control unit for active or historic diagnostic trouble codes such as C1604 or C1608
  • Inspect the rear subframe actuator rack and rubber gaiters for signs of road salt corrosion, splits, or moisture ingress
  • Drive the vehicle on a straight, flat dual carriageway at 60 to 70mph to verify straight tracking without wandering
Verified by IsItAGoodCar Research TeamUpdated

Hybrid Inverter Relay Fault and Auxiliary 12V Battery Depletion

ModerateElectrics & Electronics

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.

Est. Repair Cost: £200–£1,200
Warning Signs:

'Check Hybrid System' warning message and master warning triangle illuminated on the dashboard display, Car fails to start or enter 'Ready' status after being left parked for more than a week, Keyless entry completely unresponsive due to a flat 12V auxiliary battery, Jerky transition or shudder when the petrol V6 engine restarts from electric EV mode while driving

What to Inspect:
  • Test the voltage and state of health of the auxiliary 12V AGM battery located behind the boot trim panel
  • Ensure the car transitions smoothly into 'Ready' mode and drives away silently under battery power without hesitation
  • Check the hybrid inverter coolant expansion tank in the engine bay to verify proper fluid level and absence of airlocks
  • Scan the hybrid powertrain control module for historical voltage drop or inverter relay fault codes
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 2015 Infiniti Q70 (M)

  • Listen carefully for timing chain noise on cold startup on 2.2d models, as tensioner failure is a known OM651 issue
  • Check tyre tread depths across all four corners; heavy 2.2d and hybrid models wear front tyres rapidly
2011–20142016–2017
Check a 2015 Infiniti Q70 (M) by Registration