Inspection Procedure

HINT: If there is an open or short in the engine coolant temperature sensor circuit, the ECM outputs DTCs. Perform troubleshooting with the "SFI System HOW TO PROCEED WITH TROUBLESHOOTING (1ZZ-FE), HOW TO PROCEED WITH TROUBLESHOOTING (2ZZ-GE)".

1. READ VALUE OF HAND-HELD TESTER 
   1. Operate the hand-held tester according to the steps on the display and select "DATA LIST".

      ECM:

      DATA LIST (ECM)
      
      

      Item	Measurement Item Range (Display)	Normal Condition	Diagnostic Note
      Coolant Temp	Coolant temperature Min.:-40°C (-40°F),Max.:140°C(284°F)	After warming up:80to95°C(176 to203°F)	If the value is "-40°C (-40°F)" or "140°C (284°F)", sensor circuit is open or shorted.

      OK: Coolant temperature displayed on the tester is between 80°C (176°F) and 95°C (203° F) after warning up. 

   1. NG: GO TO ENGINE CONTROL SYSTEM (SEE  HOW TO PROCEED WITH TROUBLESHOOTING  (1ZZ-FE),  HOW TO PROCEED WITH TROUBLESHOOTING  (2ZZ-GE)) 
   2. OK: GO TO NEXT STEP 
2. INSPECT COMBINATION METER ASSY 

   INSPECTION USING OSCILLOSCOPE 

   1. Check the input signal wave form.
      1. Remove the combination meter with connectors still connected.
      2. Connect the oscilloscope to terminal C9-8 and body ground.
      3. Start the engine.
         Fig 1: Inspecting Combination Meter Assy

         Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      4. Check the signal wave form according to the conditions) in the table below.
         SIGNAL WAVE FORM CONDITION
         
         

         Item	Condition
         Tool setting	5V/DIV, 10ms/DIV
         Vehicle condition	Ignition switch ACC or ON

         OK: As shown in the illustration 

         Fig 2: Identifying Signal Wave Form

         Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. NG: Go to step 3 
   2. OK: GO TO NEXT STEP 

      REPLACE COMBINATION METER ASSY (SEE  COMBINATION METER ASSY  ) 

3. CHECK HARNESS AND CONNECTOR (BETWEEN COMBINATION METER ASSY AND ECM) (SEE  HOW TO PROCEED WITH TROUBLESHOOTING  ) 
   1. Disconnect the C9 and E5 connectors.
   2. Measure the resistance according to the value (s) in the table below.

      Standard:

      TESTER CONNECTION SPECIFIED CONDITION
      
      

      Tester Connection	Condition	Specified Condition
      C9-8-E5-14	Always	Below 1 Ω
      C9-8 - Body ground	Always	10 kΩ or higher

      Fig 3: Checking Harness And Connector (Between Combination Meter Assy And ECM)

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 
   2. OK: GO TO NEXT STEP 

      GO TO ENGINE CONTROL SYSTEM (SEE  HOW TO PROCEED WITH TROUBLESHOOTING  (1ZZ-FE),  HOW TO PROCEED WITH TROUBLESHOOTING  (22Z-GE))