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Inspection Procedure 2: Power supply circuit system
 
 
 
 
OPERATION
To SRS-ECU, the power is supplied from two independent circuits (fuse No. 16) via IG1 relay of ETACS-ECU.
If the power is not supplied to SRS-ECU, the communication between scan tool (M.U.T.-IIISE) and SRS-ECU cannot be established.
 
 
PROBABLE CAUSES
  • Damaged wiring harness and connectors
  • Battery failure
  • Malfunction of the charging system
  • Malfunction of SRS-ECU
 
 
DIAGNOSIS
STEP 1. Fuse No. 16 check.
Is the fuse in good condition?
Go to Step 3.
Go to Step 2
 
STEP 2. Fuse open circuit check
(1) Replace the fuse.
(2) Turn the ignition switch to the "ON" position, wait for at least one minute, and then turn the switch "LOCK" (OFF).
(3) Check the fuse.
Is the fuse in good condition?
Go to Step 3.
Repair the wiring harness IG1A line between the ETACS-ECU connector and the SRS-ECU connector, and replace the fuse.
 
STEP 3. Resistance measurement at the SRS-ECU connector.
(1) Disconnect the SRS-ECU connector.
(2) Take the measurements below at the SRS-ECU wiring harness side connectors.
  • Continuity GND2 line between SRS-ECU wiring harness side connector and body ground
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 4.
Repair the wiring harness GND2 line between the SRS-ECU connector and the ground.
 
STEP 4. Voltage measurement at the SRS-ECU connector.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Disconnect the SRS-ECU connector.
(3) Connect the negative battery terminal.
(4) Ignition switch: ON
(5) Take the measurements below at the SRS-ECU harness side connector.
  • Voltage between IG1A line and body ground
OK: 9 volts or more
(6) Disconnect the negative battery terminal.
Is the check result normal?
Go to Step 6.
Go to Step 5.
 
STEP 5. Resistance measurement at the SRS-ECU connector.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Disconnect the ETACS-ECU connector.
(3) Disconnect the SRS-ECU connector.
(4)
  • Continuity IG1A line between ETACS-ECU connector and SRS-ECU connector
OK: The resistance should be 2 ohms or less
Is the check result normal?
Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ).
Repair the wiring harness IG1A line between the ETACS-ECU connector and the SRS-ECU connector.
 
STEP 6. Trouble symptom check.
Is the communication between scan tool (M.U.T.-IIISE) and SRS-ECU possible?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace SRS-ECU (Refer to ).