Inspection Procedure

HINT: Read freeze frame data using a hand-held tester or OBD II scan tool. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.

1. CHECK COOLING SYSTEM 
   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.
   1. NG: REPAIR OR REPLACE COOLING SYSTEM 
   2. OK: GO TO NEXT STEP 
2. INSPECT THERMOSTAT (See  INSPECTION  ) 
   1. Remove the thermostat (see THERMOSTAT (1ZZ-FE) ).
   2. Check the valve opening temperature of the thermostat.

      Standard: 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 (see THERMOSTAT (1ZZ-FE) ).
   1. NG: REPLACE THERMOSTAT (See  THERMOSTAT (2ZZ-GE)  ) 
   2. OK: GO TO NEXT STEP 
3. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128) 
   1. Connect a hand-held tester or OBD II scan tool to the DLC3.
   2. Turn the ignition switch to ON.
   3. Turn the tester or scan tool ON.
   4. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   5. Read DTCs.
   6. If using an OBD II scan tool, refer to the instruction manual .

      Result: 

      DTC OUTPUT RESULT
      
      

      Display (DTC Output)	Proceed To
      P0128	A
      P0128 and other DTCs	B

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

   1. B: GO TO  DIAGNOSTIC TROUBLE CODE CHART  
   2. A: GO TO NEXT STEP 

      REPLACE ECM (See  ECM (1ZZ-FE/2ZZ-GE) REPLACEMENT  )