Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

2008 Toyota Prius BaseFACTORY OEM SERVICE PROCEDURE

Inspection Procedure

READ OUTPUT DTC

Connect Techstream to the DLC3.
Turn the power switch ON (IG) and turn the tester on.
Select the following menu items: Powertrain / Engine and ECT / Trouble Code.

Read the DTCs.

Result

RESULT CHART

Display (DTC Output)	Proceed To
P0116	A
P0116 and other DTCs	B

B: GO TO DTC CHART

A: Go To Next Step

INSPECT THERMOSTAT
1. Remove the thermostat (see REMOVAL ).
2. Measure the valve opening temperature of the thermostat.
  Standard temperature:
  
  80°C to 84°C (176°F to 183°F)
  
  HINT:
  
  In addition to the above check, confirm that the valve is completely closed when the temperature is below the standard.
3. Reinstall the thermostat (see INSTALLATION ).
NG: REPLACE THERMOSTAT

OK: REPLACE ENGINE COOLANT TEMPERATURE SENSOR

Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.