Inspection Procedure

HINT:

Read freeze frame data using the Techstream. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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 OTHER DTC OUTPUT (IN ADDITION TO DTC P0128) 
   1. Connect the Techstream to the DLC3.
   2. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   3. Read the current codes.

      Result 

      RESULT CHART
      
      

      Display (DTC output)	Proceed to
      P0128	A
      P0128 and other DTCs	B

      HINT:

      If any other codes besides P0128 are output, perform the troubleshooting for those DTCs first.

      B: GO TO RELEVANT DTC CHART 

      A: Go to Next Step 

2. CHECK COOLING SYSTEM 
   1. Check for defects in the cooling system that might cause the system to be too cold, such as an abnormal radiator fan operation or a modified cooling system.
   2. Check the valve opening temperature of the thermostat.

      OK: 

      Valve opening temperature is 80 to 84°C (176 to 183°F) 

      HINT:

      Also check that the valve is completely closed below the opening temperature shown above.

      NG: REPAIR OR REPLACE COOLING SYSTEM 

      OK: Go to Next Step 

3. INSPECT THERMOSTAT 
   1. Inspect the thermostat (see THERMOSTAT ).

      NG: REPLACE THERMOSTAT 

      OK: REPLACE ECM