Owners describe a range of electrical faults across the 2016 Metris. The most dangerous involves the factory tow package: the wiring harness includes a 7-pin connector but is wired for only 6 pins, controlling brake lights and signals but not electric trailer brakes. Mercedes confirmed there is no factory or aftermarket fix. One owner nearly collided on the highway when traffic stopped suddenly; the trailer brakes never activated, extending stopping distance beyond safe limits.
Wiring harness chafing is also documented. One owner's seatbelt pretensioner harness wore through its insulation at the factory-routed path despite no vehicle modifications, shorting the airbag circuit. Dealership service notes suggest this is a recurring repair.
Battery failure represents the most acute hazard: one owner's battery caught fire and melted under the passenger seat after parking, producing billowing smoke that required fire department intervention to prevent complete vehicle fire. All electronics went dead when the owner attempted restart.
Other electrical complaints include a mechanical speedometer that reads 20 mph slow and slowly drops to zero after highway driving (resolved only after stopping), a rearview camera that freezes while backing, dashboard digital display failure, and intermittent blind spot alerts and door locks tied to one side of the vehicle. Two wheel speed sensor failures disabled ABS and transmission separately.
Failure modes owners describe
Trailer brake wiring incompleteness
Factory tow package includes a 7-wire connector wired for only 6 conductors. Harness controls brake lights, turn signals, and running lights but does not operate electric trailer brakes. Mercedes acknowledges no factory or third-party solution exists. Owners assume brakes are activated when they are not, creating a safety hazard; without trailer brakes, safe towing payload is limited to approximately 2500 lbs, not the advertised 5000 lbs.
When: Factory installation; discovered when owner attempted towing
Symptoms owners cite: Trailer brake lights function but electric brakes do not activate; Increased stopping distance while towing at highway speed; Near-accident due to inability to stop quickly
Repairs/costs cited: Mercedes stated no way to activate electric brakes exists; no fix available
Recalls/TSBs owners mention: Mercedes confirmed there is no factory or third-party option to enable electric trailer brake operation
Seatbelt pretensioner wiring harness chafing
Factory-installed wiring harness for seatbelt pretensioner wore through insulation at its normal routed location despite no modifications to the vehicle. Three of four wires had insulation damaged, shorting the circuit and illuminating the airbag warning light. Dealership video documented the issue. Dealership service notes suggest this is a recurring problem they have repaired multiple times.
When: Not specified; discovered during routine operation
Symptoms owners cite: Airbag warning light illuminated; Visible wire insulation damage and fraying at normal harness path
Repairs/costs cited: Dealership repaired the issue; owner indicates dealership service records suggest repeated repairs of same issue
Dashboard digital display failure
Digital display on dashboard suddenly ceases to function. Owner reports this as part of broader quality control issues, noting frequent recalls and defects uncommon in less expensive vehicles.
When: Not specified
Symptoms owners cite: Digital dashboard display disappears without warning
Battery fire and meltdown
Battery located under passenger seat caught fire and melted approximately 2 to 2.5 hours after vehicle was parked following 2.5 to 3 hours of operation. All electronics went dead, vehicle would not start, smoke appeared from under passenger seat where battery is housed. Fire department responded; battery was literally melting. Firefighters disconnected battery to prevent complete vehicle fire.
When: After 2.5-3 hours of operation on 12/26, then parked for 2 hours before ignition attempt
Symptoms owners cite: All electronics dead, no crank; Smoke from passenger seat area; Battery melting and deteriorating
Repairs/costs cited: Fire department intervention required to disconnect battery
Mechanical speedometer malfunction
Mechanical/analog speedometer displays incorrect speed following extended highway driving (60+ mph). Gauge reads approximately 20 mph slower than actual speed, then gradually drops to zero over approximately 15 minutes. After vehicle comes to complete stop, speedometer functions normally. Digital speed displays remain accurate. Owner reports this has occurred at least 10 times. Digital cluster is unaffected.
When: Occurs after driving 60+ mph; mileage 14,000 miles reported on this vehicle
Symptoms owners cite: Mechanical speedometer reads 20 mph slow after highway driving; Gradual further drop to 0 mph over 15 minutes; Digital display remains accurate throughout; Reset after vehicle stops completely
Rearview camera image freeze
Rearview camera display froze (static image) while vehicle was backing up, making it impossible to see actual rear surroundings. Issue persisted through multiple backup attempts then resolved after parking in garage for several hours. Owner concerned about recurring malfunction and accident risk from misleading camera display.
When: Intermittent; resolved after parking in garage for hours
Symptoms owners cite: Camera display shows static frozen image while vehicle moving in reverse; Display does not update with actual vehicle surroundings; Issue resolves after extended parking
Crankcase ventilation valve malfunction
Check engine light triggered by diagnostic codes P052E71 (crankcase ventilation valve malfunction, actuator blocked) and P06DA00 (oil pump valve actuation electrical fault or open circuit). Owner reports these codes are prolific across Metris forums, indicating a widespread issue. Repair is expensive and can potentially cause catastrophic engine damage if left unaddressed.
When: Not specified; reported on multiple vehicles with low mileage
Symptoms owners cite: Check engine light illuminated
Codes mentioned: P052E71, P06DA00
Repairs/costs cited: Repair cost described as extremely high; warranty does not cover on commercial vans (covered on passenger vans with same engine)
Intermittent blind spot and door lock electrical fault
Intermittent electrical failure affecting blind spot alert system, turn signal indicator on same side, and automatic door locks on same side (appears to be one side of vehicle). System intermittently reboots and functions for periods before failure recurs. Owner describes failures as frequent despite being intermittent.
When: Intermittent; multiple recurrences reported
Symptoms owners cite: Blind spot alert inoperable; Turn signal indicator on affected side inoperative; Automatic door locks on affected side inoperative; Intermittent system reboots with temporary functionality restoration
Wheel speed sensor failures
Two separate wheel speed sensor failures reported. Right front sensor failure caused vehicle computer to disable antilock braking system. Left rear sensor failure caused transmission to enter limp mode. Both failures disabled critical vehicle safety and drivetrain systems.
When: Not specified; two separate incidents reported
Symptoms owners cite: Right front sensor: ABS disabled; Left rear sensor: transmission enters limp mode
Repairs/costs cited: Sensors required replacement
Synthesized from 10 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.