The 2016 Highlander electrical issues span power delivery, sensor operation, and safety systems. Owners report the engine starting on its own while parked, sometimes with a fuel pump running for hours after shutdown. More alarming: the vehicle loses all electrical power while driving—engine stalls, instrument displays go black or flicker, steering locks, and the liftgate won't unlock. Dealers replaced batteries on affected vehicles, but the failures returned intermittently. One vehicle caught fire from an electrical short circuit shortly after an oil change.
Sensor malfunctions create chronic distractions: rain-sensing wipers activate on clear sunny days, the cruise control display flickers on without input, and the pre-collision system beeps and warns of vehicles that aren't there. Dashboard warning lights falsely indicate the hood is open, and the navigation system activates itself with reversed map orientation.
Additional complaints include the parking sensors cutting out while backing, the liftgate closing without safety reversal, and a main wiring harness chewed by rodents (dealer noted organic-based oil on the wires attracted them). One owner reported an iPhone 11 unable to connect for hands-free calling. These failures cluster around the 35,000 to 48,000 mile mark in several cases, though diagnostics and repairs remain elusive across dealerships.
Failure modes owners describe
Engine cranks or runs without key input
Engine starts on its own while vehicle is parked and off, without driver input. One owner also reported fuel pump running hours after engine shutdown.
When: While parked; fuel pump can run 10 to 60+ minutes after shutdown, intermittently
Symptoms owners cite: Engine running when owner returns to parked vehicle; Fuel pump running in garage hours after shutdown; Yellow caution light flashing on dashboard; Loud noise when ignition engaged
Electrical system power loss / battery voltage failure
Vehicle loses electrical power affecting multiple systems—engine stalls while driving, displays flicker or shut off, steering locks, liftgate won't open, fob unlock fails, vehicle won't start. Dealer replaced battery but problem recurs intermittently.
When: While driving at various speeds; intermittent; mileage unknown to ~48,000 miles
Symptoms owners cite: Engine shuts off without warning while driving; All instrument and electronic displays shut off or flicker; Steering wheel locks and vibrates; Liftgate does not open; Vehicle cannot be unlocked with fob; Vehicle will not start or starts after multiple attempts; Trunk power switch fails to function; trunk door stuck
Repairs/costs cited: Battery replacement attempted but failure reoccurred intermittently
Recalls/TSBs owners mention: Manufacturer and dealer sided with diagnostic fee requirement; dealer blamed and replaced battery
Fire / short circuit
Vehicle caught fire while parked after routine oil change. Fire department investigator certified it was caused by a short circuit in electrical system.
When: April 2022, shortly after oil change in early March 2022; vehicle had 5 months ownership
Symptoms owners cite: Vehicle fire while parked; No warning lights on dashboard before fire
Sensor malfunction—rain-sensing wipers
Rain-sensing wipers activate randomly on clear, sunny days with no moisture present. Wipers engage intermittently while driving, causing distraction.
When: While driving; intermittent
Symptoms owners cite: Wipers activate on clear days with sun shining; Wipers engage randomly and repeatedly while driving; Severe distraction to driver
Sensor malfunction—active cruise control display
Cruise control display and settings activate randomly while driving with no vehicles in front of the vehicle. Display flickers between normal and set screens intermittently.
When: While driving on freeway; intermittent
Symptoms owners cite: Cruise control display activates with no vehicles nearby; Display flickers back and forth between normal and set screens; Distracting while driving on freeway
Pre-collision system malfunction
Pre-collision system activates randomly with no vehicles nearby. Warning light illuminates on dash accompanied by rapid beeping, causing driver distraction and potential safety hazard.
When: While driving city streets and freeway, while coasting and accelerating; intermittent
Symptoms owners cite: Pre-collision warning activates with no other vehicles nearby; Dash warning light and rapid beeping; Can occur while changing lanes; Documented on dashcam
Interior lighting and gauge cluster malfunctions
Interior lights turn on and off intermittently. Dashboard warning lights, including false 'hood open' warnings, illuminate when conditions do not exist. Navigation system turns on by itself with incorrect directions and inverted map orientation.
When: While vehicle in motion; intermittent
Symptoms owners cite: Interior lights cycling on and off; False 'hood open' warning when hood is closed; Navigation system activates without input; Map directions incorrect and inverted (north shown as south, east as west); Dashboard module cracked during service
Repairs/costs cited: Dashboard module cracked by technician during phone number deletion attempt
Bluetooth / phone compatibility issue
iPhone 11 not compatible with vehicle infotainment system. Audio disconnects every time phone connects to vehicle, preventing hands-free calling while driving.
When: Upon vehicle startup and phone connection; repeats on every startup
Symptoms owners cite: Car audio disconnects when iPhone 11 connects; Unable to drive hands-free; Phone listed as incompatible on Toyota website
Wiring harness damage—rodent chew
Main wiring harness damaged and chewed by rodents. Check engine light illuminated and AWD system ceased functioning. Dealer noted organic-based oil on harness wires attracts rodents.
When: Mileage unknown
Symptoms owners cite: AWD system stopped working; Check engine light illuminated; Main wiring harness found chewed by rodents
Repairs/costs cited: Main wiring harness damage caused by rodent chewing; dealer attributed to organic-based oil on wires
Parking sensors and park assist failure
Parking sensors and park assist system randomly disable. Sensors stop detecting objects while backing up and dash indicator light turns off.
When: While backing and parking; intermittent
Symptoms owners cite: Parking sensors fail to detect obstacles; Park assist system disables; Dash indicator light not illuminated when disabled
Liftgate uncontrolled closure
Liftgate closed on occupant without reversing or stopping, striking elderly passenger in head. No safety feature prevented or arrested the door closure.
When: Incident date unknown; mileage unknown
Symptoms owners cite: Liftgate closed on occupant; No safety reversal or stop mechanism activated; Struck 73-year-old passenger in head
Synthesized from 14 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.