Reset high coolant temperature warning light Toyota Prius

Reset high coolant temperature warning light Toyota Prius second generation XW20. From year: 2003, 2004, 2005, 2006, 2007, 2008.

How to reset high coolant temperature warning light Toyota Prius.

The light operates to warn that the hybrid system is almost overheating. If it comes on while you are driving, stop the vehicle and check your hybrid system. For detailed instructions, see “If your vehicle overheats” below in this section.

Your vehicle may overheat during severe operating conditions, such as:

  • Driving up a long hill on a hot day.
  • Reducing speed or stopping after high speed driving.

Do not remove the thermostat in the cooling system as this may cause the hybrid system to overheat. The thermostat is designed to control the flow of coolant to keep the temperature of the hybrid system within the specified operating range.

Continued driving with the light on could result in the overheating of hybrid system.

If your Toyota Prius is overheats.

If your high coolant temperature warning light comes on, if you experience a loss of power, or if you hear a loud knocking or pinging noise, the hybrid system has probably overheated. You should follow this procedure.

  1. Pull safely off the road, stop the vehicle and turn on your emergency flashers. Push the “P” position switch and apply the parking brake. Turn off the air conditioning if it is being used.
  2. If coolant or steam is boiling out of the radiator or reservoir, stop the hybrid system. Wait until the steam subsides before opening the hood. If there is no coolant boiling over or steam, leave the hybrid system running and make sure the electric cooling fan is operating. If it is not, turn the hybrid system off. To help avoid personal injury, keep the hood closed until there is no steam. Escaping steam or coolant is a sign of very high pressure.
  3. Look for obvious coolant leaks from the radiator, hoses, and under the vehicle. However, note that water draining from the air conditioning is normal if it has been used. When the hybrid system is running, keep hands and clothing away from the moving fan and engine drive belts.
  4. If the coolant is leaking, stop the hybrid system immediately. Call a Toyota dealer for assistance.
  5. If there are no obvious leaks, check the coolant reservoir. If it is dry, add coolant to the reservoir while the hybrid system is running. Fill it about half full. Do not attempt to remove the radiator cap when the hybrid system and radiator are hot. Serious injury could result from scalding hot fluid and steam blown out under pressure.
  6. After the coolant temperature has cooled to normal, again check the coolant level in the reservoir. If necessary, bring it up to half full again. Serious coolant loss indicates a leak in the system. You should have it checked as soon as possible at your Toyota dealer.


That it is the full procedure how to reset high coolant temperature warning light Toyota Prius second generation XW20. If you like to reset any maintenance oil light after an oil change. Or reset check engine light, airbag light, inspection key or insp errors when maint reqd, for Toyota cars. Or any warning light for service reminder which appears on the display. Write in the search box the car name for which you want to find information, and find how to reset other service reminders by yourself.  

This is an information site where you can solve your car problems. Send us a comment if our procedures are correctly. If you would have anything to add, for us every opinion counts.

Click hear to see full procedure how do you reset the oil light indicator. How to reset the maintenance light and how do you reset service light for all Toyota vehicles.


4 thoughts on “Reset high coolant temperature warning light Toyota Prius”

  1. Thomas Murphy

    My light keeps coming on. I have had the system purged and a new thermostat install. There are no leaks anywhere. The system was pressure tested twice. No leaks. What do you think???

      1. Michael Kessler

        I am have the same problem and I had both temp sensors changed and it didn’t help. Did resetting fix the problem for you?

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