DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
5. Read the DTCs.

   Result

   Result	Proceed to
   DTC P0128 is output	A
   DTC P0128 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0128 are output, troubleshoot those DTCs first.

B → See step   4 

A: Go to next step 

1. Check for defects in the cooling system that might cause the system to be too cold, such as abnormal radiator fan operation or any modifications.

NG → See step   5 

OK: Go to next step 

1. Remove the thermostat . Refer to REMOVAL .
2. Measure the valve opening temperature of the thermostat.

   Standard value

   80 to 84°C (176 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 . Refer to INSTALLATION .

NG → See step   6 

OK → See step   7