Inspection Procedure 1: Power supply to the TCU fails [Cannot communicate with TCU using the scan tool (M.U.T.-IIISE)]: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe

1. STEP 1. Voltage measurement at the TCU connector (+B terminal). 
   1. Disconnect the TCU connector, and measure at the wiring harness side.
   2. Check the voltage between the TCU connector (+B terminal) and body ground.

      OK: The voltage should measure approximately 12 volts (battery positive voltage). 

      Q: Is the check result normal? 

      YES:  Go to Step  2.

      NO:  Repair the connector(s) or wiring harness.

2. STEP 2. Voltage measurement at the TCU connector (IG terminal). 
   1. Disconnect the TCU connector, and measure at the wiring harness side.
   2. Turn the ignition switch from OFF position to ON position.
   3. Check the voltage between the TCU connector (IG terminal) and body ground.

      OK: The voltage should measure approximately 12 volts (battery positive voltage). 

      Q: Is the check result normal? 

      YES:  Go to Step  3.

      NO:  Repair the connector(s) or wiring harness.

3. STEP 3. Resistance measurement at the TCU connector (GND, GND2 terminals). 
   1. Disconnect the TCU connector, and measure at the wiring harness side.
   2. Measure the resistance between the TCU connector (GND terminal) and body ground.

      OK: The resistance should be 2 ohms or less 

   3. Measure the resistance between the TCU connector (GND2 terminal) and body ground.

      OK: The resistance should be 2 ohms or less 

      Q: Is the check result normal? 

      YES:  Go to Step  4.

      NO:  Repair the connector(s) or wiring harness.

4. STEP 4. Retest the system. 

   Q: Is the check result normal? 

   YES:  The trouble can be an intermittent malfunction (Refer to How to use Troubleshooting/inspection Service Points - HOW TO COPE WITH INTERMITTENT MALFUNCTION ).

   NO:  Replace the TCU (Refer to TCU  ).