The 2017 Sonata PHEV combines Hyundai's 2.0L Theta II turbo engine with a 67-hp electric motor and 9.8 kWh battery. While the hybrid system itself is relatively robust, the gasoline engine suffers from catastrophic oil consumption and bearing failure issues that plague the entire Theta II family—warranty extensions exist, but many owners still face expensive rebuilds.
Theta II Engine Bearing Failure and Oil Consumption
Common · high severity
Typical onset: 60,000-100,000 mi
Symptoms: Excessive oil consumption (1 quart per 1,000 miles or worse), Metallic knocking from crankshaft area, especially cold starts, Check engine light with misfire codes or low oil pressure warning, Sudden catastrophic failure resulting in seized engine
Fix: Full engine replacement or short block replacement required in most cases. Hyundai extended warranty to 10yr/100k miles for original owners on many Theta II engines after class-action settlements, but second owners often aren't covered. Independent rebuild takes 20-30 labor hours; dealer replacement 15-20 hours with remanufactured unit.
Estimated cost: $5,500-9,000
Transmission Oil Cooler Line Leaks
Occasional · medium severity
Typical onset: 70,000-110,000 mi
Symptoms: Transmission fluid puddles under vehicle, typically passenger side, Burnt transmission fluid smell after highway driving, Erratic shifting or slipping when fluid level drops significantly, Pink or red fluid visible on cooler lines near radiator
Fix: Replace transmission cooler lines and associated seals. The 6-speed automatic used in this PHEV has external cooler lines that corrode at crimp points. Job requires lowering front subframe for access in some cases. 3-5 labor hours depending on line routing complexity.
Estimated cost: $450-850
Engine and Transmission Mount Deterioration
Common · low severity
Typical onset: 80,000-120,000 mi
Symptoms: Excessive vibration during electric-to-gas engine transitions, Clunking when shifting from Park to Drive or Reverse, Visible engine movement when revving in Park, Increased cabin noise during acceleration
Fix: The added weight of the battery pack and hybrid components accelerates mount wear. Typically need to replace upper engine mount and front transmission mount as a pair. 2-3 labor hours with proper lifting equipment.
Estimated cost: $350-650
12V Auxiliary Battery Premature Failure
Occasional · medium severity
Symptoms: Vehicle won't enter 'Ready' mode despite charged high-voltage battery, Clicking from under hood when pressing start button, Warning messages about hybrid system malfunction, Completely dead electrical system after sitting 2-3 days
Fix: The 12V battery powers computers and engages the hybrid system contactors—when it fails, you're stranded even with a full traction battery. Many fail at 3-4 years instead of typical 5-6. Replacement requires hybrid system shutdown procedure and computer reset. 1 labor hour including registration with BCM.
Estimated cost: $250-400
High-Pressure Fuel Pump Failure
Occasional · high severity
Typical onset: 90,000-130,000 mi
Symptoms: Hard starting or extended cranking, especially when engine is hot, Loss of power under acceleration when gasoline engine engages, P0087 code (fuel rail pressure too low), Engine running roughly after transitioning from EV mode
Fix: The direct-injection high-pressure pump on the Theta II is engine-mounted and can fail from contaminated fuel or internal wear. Replacement requires removing intake manifold for access. Metal debris from failing pump can contaminate injectors, requiring full fuel system cleaning. 4-6 labor hours.
Estimated cost: $1,200-1,800
Charge Door Actuator and Latch Failures
Occasional · low severity
Typical onset: 50,000-90,000 mi
Symptoms: Charge port door won't unlock or open when button pressed, Door pops open randomly while driving, Grinding noise from rear quarter panel when attempting to open, Warning message about charge door malfunction
Fix: The motorized charge door mechanism uses plastic gears that strip over time, especially in cold climates. Requires removal of rear bumper cover or inner fender liner for access. Dealer-only part in most cases. 2-3 labor hours.
Estimated cost: $400-700
Owner tips
Check engine oil level every 1,000 miles religiously—if consumption exceeds 1 quart per 1,500 miles, document it and pursue warranty claim immediately before catastrophic failure
Keep records of all oil changes and maintenance for potential engine warranty claim; Hyundai has been denying claims for owners without perfect documentation
Replace 12V auxiliary battery preventively at 4 years to avoid being stranded—it's cheap insurance on a hybrid
Use only Top Tier gasoline to minimize direct-injection carbon buildup and high-pressure fuel system contamination
Avoid unless you're the original owner with engine warranty coverage intact—the Theta II engine is a ticking time bomb, and a post-warranty failure will exceed the car's remaining value.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
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Fitment notes: AGM battery required for PHEV system; located in trunk
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Every control module on the 2016-2019 Hyundai Sonata Plug-in Hybrid — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Mileage programming required; VIN and vehicle configuration must be written
Immobilizer Control Unit (IMM)0.8 hr R&Rdealer / factory tool +0.6 hr▸ programming details
📍 Integrated with ignition switch assembly or separate module near steering column
🔧 Hyundai GDS
⚠️ Key programming and ECM synchronization required
Fuel Pump Control Module (FPCM)0.6 hr R&Rrelearn only +0.1 hr▸ programming details
📍 Under rear seat or in trunk area near fuel tank
🔧 Self-learning via drive cycle
Rear View Camera Module (RVC)0.5 hr R&Rno coding
📍 Integrated with rear camera in trunk lid handle area
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Hyundai Motor America (Hyundai) is recalling certain 2015-2017 Sonata, 2016-2017 Sonata Hybrid, and Sonata Plug-In Hybrid vehicles. The Smart Junction Box (SJB) software logic may not properly interpret the signals received from the multifunction switch, which could cause the turn signal to activate in the opposite direction of what the driver intended.
Consequence: A turn signal that activates in the opposite direction of what was intended by the driver increases the risk of a crash.
Remedy: Dealers will update the SJB software, free of charge. Owner notification letters were mailed November 19, 2021. Owners may contact Hyundai customer service at 1-855-371-9460. Hyundai's number for this recall is 210.
Hyundai Motor America (Hyundai) is recalling certain 2017-2018 Sonata, 2016-2018 Sonata Hybrid, 2018-2020 Accent, and 2016-2017 Azera vehicles. The trunk latch may become damaged, preventing the opening of the trunk from the inside. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 401, "Internal Trunk Release."
Consequence: A person inside the trunk compartment may become trapped, increasing their risk of injury.
Remedy: Dealers will replace the trunk latch base, free of charge. Owner notification letters were mailed December 4, 2021. Owners may contact Hyundai customer service at 1-855-371-9460. Hyundai's number for this recall is 208.
HYBRID PROPULSION SYSTEM · 18V166000
2018-03-12
Hyundai Motor America (Hyundai) is recalling certain 2016-2018 Hyundai Sonata Plug-In Hybrid vehicles. These vehicles are equipped with a Voltage Protection Device (VPD), designed to protect the high voltage battery module, that may activate inadvertently.
Consequence: If the VPD activates while the vehicle is being operated in Electric Vehicle (EV) mode, there may be a loss of power, increasing the risk of a crash.
Remedy: Hyundai will notify owners, and dealers will remove the VPD switch and install a new Battery Management System (BMS) that contains an Overvoltage Protection Device (OPD). The recall is expected to begin May 2018. Owners may contact Hyundai customer service at 1-855-371-9460. Hyundai's number for this recall is 175.
AIR BAGS:FRONTAL:DRIVER SIDE:INFLATOR MODULE · 16V956000
2016-12-30
Hyundai Motor Company (Hyundai) is recalling certain model year 2017 Hyundai Elantra vehicles manufactured April 15, 2016, to September 13, 2016, and Sonata vehicles manufactured May 27, 2016 to September 16, 2016. In these vehicles, the end seal for the driver's frontal air bag inflator may not have been properly installed, possibly resulting in reduced inflation of the frontal air bag in the event of a crash.
Consequence: In the event of a crash, an air bag that does not inflate fully increases the risk of injury.
Remedy: Hyundai will notify owners, and dealers will replace the driver's frontal air bag module, free of charge. The recall began February 13, 2017. Owners may contact Hyundai customer service at 1-855-371-9460. Hyundai's number for this recall is 156.
Fuel economy (EPA)
City
38mpg
Highway
40mpg
Combined
39mpg
Fuel
Regular Gasoline
Capability & size
EPA class
Midsize Cars
Wiper blades
7th generation (LF) Sonata - sedan body style has no rear wiper
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2017 Hyundai Sonata Plug-in Hybrid 2.0L I4 PHEV and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.