Lexus RX Owners Manual (RX450h): If the 12-volt battery is discharged

The following procedures may be used to start the hybrid system if the vehicle's 12-volt battery is discharged.

You can also call your Lexus dealer or a qualified repair shop.

If you have a set of jumper (or booster) cables and a second vehicle with a 12-volt battery, you can jump start your vehicle by following the steps below.

1. Confirm that the electronic key is being carried.

When connecting the jumper (or booster) cables, depending on the situation, the alarm may activate and doors locked.

Lexus RX. Steps to take in an emergency

2. Open the hood and fuse box cover.

Lexus RX. Steps to take in an emergency

3. Open the exclusive jump starting terminal cover.

Lexus RX. Steps to take in an emergency

4. Remove the engine cover.

Lexus RX. Steps to take in an emergency

5. Connect the jumper cables according to the following procedure:

Lexus RX. Steps to take in an emergency

  1. Connect a positive jumper cable clamp to the exclusive jump starting terminal on your vehicle.
  2. Connect the clamp on the other end of the positive cable to the positive (+) battery terminal on the second vehicle.
  3. Connect a negative cable clamp to the negative (-) battery terminal on the second vehicle.
  4. Connect the clamp at the other end of the negative cable to a solid, stationary, unpainted metallic point away from the exclusive jump starting terminal and any moving parts, as shown in the illustration.

6. Start the engine of the second vehicle. Increase the engine speed slightly and maintain at that level for approximately 5 minutes to recharge the 12-volt battery of your vehicle.

7. Open and close any of the doors of your vehicle with the power switch off.

8. Maintain the engine speed of the second vehicle and start the hybrid system of your vehicle by turning the power switch to ON mode.

9. Make sure the "READY" indicator comes on. If the indicator light does not come on, contact your Lexus dealer.

10. Once the hybrid system has started, remove the jumper cables in the exact reverse order from which they were connected.

11. Close the exclusive jump starting terminal cover, and reinstall the fuse box cover to its original position.

Once the hybrid system starts, have the vehicle inspected at your Lexus dealer as soon as possible.

■ Starting the hybrid system when the 12-volt battery is discharged The hybrid system cannot be started by push-starting.

■ To prevent 12-volt battery discharge

  • Turn off the headlights and the audio system while the hybrid system is off.
  • Turn off any unnecessary electrical components when the vehicle is running at a low speed for an extended period, such as in heavy traffic.

■ When removing the battery terminals When the battery terminals are removed, the information stored in the ECU is cleared.

Before removing the battery terminals, contact your Lexus dealer.

■ Charging the 12-volt battery The electricity stored in the 12-volt battery will discharge gradually even when the vehicle is not in use, due to natural discharge and the draining effects of certain electrical appliances.

If the vehicle is left for a long time, the 12-volt battery may discharge, and the hybrid system may be unable to start. (The 12-volt battery recharges automatically while the hybrid system is operating.)

■ When the 12-volt battery is removed or discharged

  • In some cases, it may not be possible to unlock the doors using the smart access system with push-button start when the 12-volt battery is discharged. Use the wireless remote control or the mechanical key to lock or unlock the doors.
  • The hybrid system may not start on the first attempt after the 12-volt battery has recharged but will start normally after the second attempt. This is not a malfunction.
  • The power switch mode is memorized by the vehicle. When the 12-volt battery is reconnected, the system will return to the mode it was in before the 12-volt battery was discharged. Before disconnecting the 12-volt battery, turn the power switch off.

    If you are unsure what mode the power switch was in before the 12-volt battery discharged, be especially careful when reconnecting the 12-volt battery.

  • The power back door must be initialized.

■ When replacing the 12-volt battery

  • RX450h: Use a Central Degassing type 12-volt battery (European Regulations).

    RX450hL: Use a 12-volt battery designed for this vehicle.

  • RX450h: Use a 12-volt battery that the case size is same as the previous one (LN2), 20 hour rate capacity (20HR) is equivalent (60Ah) or greater, and performance rating (CCA) is equivalent (460A) or greater.
    • If the sizes differ, the 12-volt battery cannot be properly secured.
    • If the 20 hour rate capacity is low, even if the time period where the vehicle is not used is a short time, the 12-volt battery may discharge and the hybrid system may not be able to start.
  • Use a 12-volt battery with a handle. If a 12-volt battery without a handle is used, removal is more difficult.
  • After replacing, firmly attach the following items to the exhaust hole of the 12-volt battery.
    • Use the exhaust hose that was attached to the 12-volt battery before replacing and confirm that it is firmly connected to the hole section of the vehicle.
    • Use the exhaust hole plug included with the 12-volt battery replaced or the one installed on the 12-volt battery prior to the replacement.

      (Depending on the 12-volt battery to be replaced, the exhaust hole may be plugged.)

      1. Exhaust hole plug
      2. Exhaust hole
      3. Exhaust hose
      4. Hole section of the vehicle


Lexus RX. Steps to take in an emergency


Lexus RX. Steps to take in an emergency

For details, consult your Lexus dealer.


■When removing the battery terminals Always remove the negative (-) terminal first. If the positive (+) terminal contacts any metal in the surrounding area when the positive (+) terminal is removed, a spark may occur, leading to a fire in addition to electrical shocks and death or serious injury.


■ Avoiding 12-volt battery fires or explosions Observe the following precautions to prevent accidentally igniting the flammable gas that may be emitted from the 12-volt battery:

  • Make sure each jumper cable is connected to the correct terminal and that it is not unintentionally in contact with any other than the intended terminal.
  • Do not allow the other end of the jumper cable connected to the "+" terminal to come into contact with any other parts or metal surfaces in the area, such as brackets or unpainted metal.
  • Do not allow the + and - clamps of the jumper cables to come into contact with each other.
  • Do not smoke, use matches, cigarette lighters or allow open flame near the 12-volt battery.

■ 12-volt battery precautions The 12-volt battery contains poisonous and corrosive acidic electrolyte, while related parts contain lead and lead compounds. Observe the following precautions when handling the 12-volt battery:

  • When working with the 12-volt battery, always wear safety glasses and take care not to allow any battery fluids (acid) to come into contact with skin, clothing or the vehicle body.
  • Do not lean over the 12-volt battery.
  • In the event that battery fluid comes into contact with the skin or eyes, immediately wash the affected area with water and seek medical attention.

    Place a wet sponge or cloth over the affected area until medical attention can be received.

  • Always wash your hands after handling the 12-volt battery support, terminals, and other battery-related parts.
  • Do not allow children near the 12-volt battery.

■ After recharging the 12-volt battery Have the 12-volt battery inspected at your Lexus dealer as soon as possible.

If the 12-volt battery is deteriorating, continued use may cause the 12-volt battery to emit a malodorous gas, which may be detrimental to the health of passengers.

■When replacing the 12-volt battery

  • When the vent plug and indicator are close to the hold down clamp, the battery fluid (sulfuric acid) may leak.
  • For information regarding 12-volt battery replacement, contact your Lexus dealer.
  • Make sure to replace the 12-volt battery with one designed for this vehicle. Otherwise, hydrogen gas may enter the vehicle, possibly causing a fire or explosion.
  • After replacing, securely attach the exhaust hose and exhaust hole plug to the exhaust hole of the replaced 12-volt battery. If not properly installed, gases (hydrogen) may leak into the vehicle interior, and there is the possible danger of the gas igniting and exploding.


■When handling jumper cables When connecting the jumper cables, ensure that they do not become entangled in the cooling fans or belt.

■ To prevent damaging the vehicle The exclusive jump starting terminal is to be used when charging the 12-volt battery from another vehicle in an emergency. It cannot be used to jump start another vehicle.

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