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Toyota

Prius Gen 4 (2016-2022)

HEV · Hybrid207V system
10

Wait

minutes

after 12V cut before HV contact

Do not touch HV components until wait time has passed

FRONT

12V

MID

REAR

HV pack

SP
HV pack zone12V batteryHV disable loop / service plug
  • SP — Service plug — under rear seat cushion; lift seat bottom and remove HV battery fan inlet cover to access

Schematic zones only — front/mid/rear are approximate. Verify exact locations against the OEM Emergency Response Guide.

First 10 minutes — pre-flight

Before you touch the vehicle. Run this once for every inbound EV or hybrid.

  1. Park downwind, on level ground

    If the pack is in thermal runaway it will vent flammable + toxic gas. Stay upwind. Block wheels.

  2. PPE on: HV-rated gloves, safety glasses, no jewelry

    Class 0 (1000V) rubber insulating gloves with leather over-protectors are the floor for any HV work.

  3. Walk-around: damage scan + signs of pack compromise

    Coolant pooling, white smoke/vapor, hissing, bulging panels, exposed orange cables, or chemical smell = stop. Treat as live and call OEM hotline.

  4. Confirm the vehicle is this card (year, make, model)

    Pack location and disable procedure differ between generations. Use the distinguishing visual to be sure.

  5. Locate your fire suppression and first-aid kit before starting

    Water is the only effective agent on Li-ion. Dry chemical, foam, and CO₂ will not stop a runaway. Have ≥250 gallons accessible.

HV Disable

  1. Primary
    Pull the orange Service Plug Grip (service disconnect) — rotate lever and pull straight out. Wear Class 0 (1000V) HV gloves.

    Under the rear seat cushion — lift/remove the rear seat bottom cushion, then remove the HV battery fan inlet cover to expose the orange Service Plug Grip on the pack.

  2. Backup
    Power off vehicle via START button, then disconnect 12V auxiliary battery negative terminal. Remove IG2 fuse from engine-bay fuse box as additional isolation.

    12V battery — see twelveVolt.location. IG2 fuse — engine compartment fuse/relay box.

Note
HV system can remain energized for up to 10 minutes after vehicle shutdown. ALWAYS verify zero voltage with a CAT III rated meter on orange HV cables before cutting or dismantling. Pack is much smaller than a BEV but >50 V is still lethal.

12V battery & SRS

12V location: Engine compartment / under the hood (Gen 4 relocated the 12V auxiliary battery forward from the cargo area used on Gen 3 — smaller transaxle/PCU made room for an under-hood aux battery)

12V powers HV contactors and is charged by HV pack via DC-DC converter. Disconnect negative terminal AFTER pulling service plug to fully isolate. AGM-type battery — do not short. NHTSA recall 18V579000 affects the engine-bay wire harness routed near the PCU on 2016-2018 cars — inspect engine bay before any cutting.

discharge: wait 90s after airbag deployment before touching SRS components.1 source· 2×

Pack & no-cut zones

Pack location: Under the rear seat cushion (Gen 4 relocated the HV pack from the cargo area / behind-rear-seat position used on Gen 3 to underneath the rear seat). Access via the rear seat bottom cushion / HV battery fan inlet cover.

Pack chemistry: Both NiMH and Li-ion depending on trim/drivetrain. FWD trims (especially Eco) typically ship Li-ion (~0.75 kWh); AWD-e trims (MY2019+) and most base/L trims ship NiMH (~1.2-1.3 kWh). VERIFY chemistry per VIN or pack-case label before any HV work — firefighting and reignition profiles differ materially. Phase-2 work will split this card into Prius Gen 4 NiMH and Prius Gen 4 Li-ion variants.

cable color:Orange

Do not cut:

  • HV battery pack footprint (under the rear seat cushion)
  • Orange HV cable routing (runs under vehicle from under-rear-seat pack to transaxle / inverter in engine bay)
  • Inverter / Power Control Unit (PCU) in engine bay
  • SRS components (steering column, A-pillars, B-pillars, roof rails, seat-mounted side airbags, knee airbag area)
  • Hatch gas struts and any pyrotechnic pre-tensioners on seat belts
  • Fuel tank and fuel lines (still a gasoline vehicle — full HEV fuel system present)

Reinforcement (UHSS):

  • A-pillars
  • B-pillars
  • Roof rails
  • Rocker panels
  • Rear floor / rear seat pan reinforcement around HV pack

Pack piercing risk: Pack case is steel but the rear seat pan above it is thin sheet metal. Any tool penetrating the rear floor pan / rear seat area (cutoff wheel, recip saw, spreader tip) can breach a cell. NiMH cells leak corrosive KOH electrolyte if breached; Li-ion cells can vent flammable electrolyte and enter thermal runaway. ALWAYS pull the service plug before any cutting near or under the rear seat.

Isolate damaged vehicle 25 ft from exposures.

Open NHTSA recalls (10)

Live from NHTSA. Cross-check the VIN against nhtsa.gov/recalls before work.

Responder-relevant (4)

  • 19V876000 · MY 2019 · ELECTRICAL SYSTEM: INSTRUMENT CLUSTER/PANEL

    Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain 2019 Prius vehicles. An electrical short circuit in the combination meter could occur, causing the speedometer, the odometer, and the fuel gauge to go blank. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 101, "Controls and Displays."

    Remedy: Toyota will notify owners, and dealers will inspect the flash memory chip (ROM) production date, and if necessary, replace it along with the combination meter circuit board, free of charge. The recall began February 7, 2020. Owners may contact Toyota customer service at 1-888-270-9371. Toyota's numbers for this recall are 19TA21 and 19TB21.

    Filed

  • 19V544000 · MY 2019 · ELECTRONIC STABILITY CONTROL (ESC)

    Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain 2019 Lexus LS500, LC500, ES300h, UX250h, LS500h, Toyota Prius, RAV4 HV, 2019-2020 Toyota Prius Prime, and 2020 Corolla HV vehicles. The brake booster pump may fail causing a deactivation of the Vehicle Stability Control system and a loss of braking assist. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 126, "Electronic Stability Control Systems."

    Remedy: Toyota will notify owners, and dealers will inspect and, if necessary, replace the brake booster pump, free of charge. The recall began September 20, 2019. Toyota owners may contact Toyota customer service at 1-888-270-9371 and Lexus owners may contact Lexus customer service at 1-800-255-3987. Toyota's numbers for this recall are K1L/K0L. Lexus' numbers for this recall are K2F/KLF.

    Filed

Show 6 other recalls
  • 21V734000 · MY 2022 · ENGINE AND ENGINE COOLING:ENGINE:ENGINE CONTROL MODULE (ECU/ECM):SOFTWARE

    Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain 2022 Prius and Prius Prime vehicles. The Engine Control Unit (ECU) software may falsely detect an error and shut down the hybrid…

  • 19V244000 · MY 2019 · EQUIPMENT:OTHER:LABELS

    Gulf States Toyota (GST) is recalling certain 2019 C-HR, 4Runner, Avalon, Avalon Hybrid, Camry, Camry Hybrid, Highlander, Land Cruiser, Prius, RAV4, Sequoia, Tacoma, Sienna, Tundra and Yaris vehicles.…

  • 18V085000 · MY 2016 · AIR BAGS:SIDE/WINDOW

    Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain 2016 Toyota Prius and Lexus RX 350, RX 350 F Sport, RX 450h F Sport and RX 450h vehicles and 2015-2016 Lexus NX 200T, NX Turbo an…

  • 17V295000 · MY 2017 · TIRES:TEMPORARY/EMERGENCY SPARE TIRE

    Gulf States Toyota, Inc. (Gulf States) is recalling certain 2017 4Runner , 86, Avalon, Camry, Camry Hybrid, Corolla, Corolla iM, Highlander, Highlander Hybrid, Prius, Prius C, RAV4, RAV4 Hybrid, Sienn…

  • 16V741000 · MY 2016 · PARKING BRAKE

    Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain model year 2016-2017 Prius vehicles manufactured August 6, 2015, to October 3, 2016. The affected vehicles are equipped with a f…

  • 16V672000 · MY 2016 · AIR BAGS:FRONTAL:PASSENGER SIDE:INFLATOR MODULE

    Toyota Motor Engineering and Manufacturing (Toyota) is recalling certain model year 2016 Toyota Prius vehicles manufactured November 30, 2015, to June 14, 2016. An air bag inflator manufacturing erro…

Lift / jack points

Use Toyota-designated pinch-weld lift points on rocker panels only. Do NOT lift directly under the rear seat pan where the HV pack sits — risk of piercing pack case. Do NOT lift under fuel tank.

Fluid hazards

Coolant: Engine coolant — Toyota Super Long Life Coolant (pink). Inverter coolant loop — separate pink coolant loop for PCU/transaxle. HV battery itself is air-cooled, no dedicated coolant.

Electrolyte color: NiMH variants — clear to pale yellow potassium hydroxide (KOH), strongly alkaline (caustic, pH ~14). Li-ion variants — clear, flammable carbonate-based electrolyte.

If burning, toxic vapors:

  • Potassium hydroxide aerosol (NiMH variants) — caustic, severe respiratory hazard
  • Hydrogen fluoride (HF) — Li-ion variants only
  • Carbon monoxide
  • Volatile organic compounds (electrolyte solvents — Li-ion)
  • Nickel oxide / cobalt oxide / manganese oxide particulates (Li-ion NMC)
  • Hydrogen gas (NiMH overcharge / damage scenario)

Firefighting

Show firefighting details — Water (large volume). Smaller pack than a BEV — significantly less water required, but still copious flow recommended for any HV pack involvement., ~500 gal

Agent: Water (large volume). Smaller pack than a BEV — significantly less water required, but still copious flow recommended for any HV pack involvement.

Estimated volume: 500 gal

Reignition risk: 4 hours post-fire

Thermal imaging: required during monitoring

Source

Toyota Prius Gen 4 Emergency Response Guide (PDF) →

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Confirm this is your vehicle

Show distinguishing visual

Aggressive angular front fascia with split LED headlights; boomerang tail-lights wrapping rear hatch; "HYBRID SYNERGY DRIVE" or "HYBRID" badging on rear hatch and front fenders; XW50 chassis code

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