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Inspection Procedure 1: Power Supply Circuit Check
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
If the gateway-ECU (for TCU) functions do not work at all, power supply to the gateway-ECU (for TCU), or the gateway-ECU (for TCU) itself may have a problem.
 
 
TROUBLESHOOTING HINTS
  • Damaged harness wires and connectors
  • Malfunction of gateway-ECU (for TCU)
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Voltage measurement at the gateway-ECU (for TCU) connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Measure the voltage between the gateway-ECU (for TCU) connector (+B terminal) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of open circuit in +B line between the fusible link and gateway-ECU (for TCU) connector.
Is the check result normal?
Perform the battery test (Refer to GROUP 54A - Battery - Battery Test ) or check the battery terminals for looseness or contamination.
Repair the connector(s) or wiring harness.
 
STEP 3. Voltage measurement at the gateway-ECU (for TCU) connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between the gateway-ECU (for TCU) connector (IG terminal) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 6.
Go to Step 4.
 
STEP 4. Using scan tool (M.U.T.-IIISE), check other system data list.
Check the input signal from the ignition switch (IG1) in the ETACS-ECU.
  • Turn the ignition switch to the "ON" position.
 
Item No.Item nameNormal condition
79IG voltageBattery positive voltage
OK: Normal condition is displayed.
Is the check result normal?
Go to Step 5.
: Troubleshoot the ETACS-ECU (Refer to Inspection Procedure 2 "The ignition switch (IG1) signal is not received." ).
 
STEP 5. Check of open circuit in IG line between the ignition switch (IG1) and gateway-ECU (for TCU) connector.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 6. Resistance measurement at the gateway-ECU (for TCU) connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between the gateway-ECU (for TCU) connector (GND terminal) and the body ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 8.
Go to Step 7.
 
STEP 7. Check of open circuit in GND line between gateway-ECU (for TCU) connector and body ground.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 8. Retest the system
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the gateway-ECU (for TCU) (Refer to ).