Inspection Procedure 2: Power supply circuit system












OPERATION



  • The SRS-ECU is energized by the ignition switch (IG1) through multi-purpose fuse 2 and the SRS-ECU terminal 24 and multi-purpose fuse 3 and the SRS-ECU terminal 23.
  • If the power supply to the SRS-ECU has failed, M.U.T.-III will not be able to communicate with it.

PROBABLE CAUSES



  • Damaged wiring harness or connector
  • Charging system failed
  • Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. Fuse Nos. 2, 3 check.

Q. 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 OFF.
(3)Check the fuse.

Q. Is the fuse in good condition?
Go to Step 3.
Repair the wiring harness between the D-405 junction block connector (terminal No.7 and 25) and the D-24 SRS-ECU connector terminal (No. 23 and 24), and replace the fuse.

STEP 3. Resistance measurement at SRS-ECU connector D-24.
(1)Disconnect the negative battery terminal.
(2)Disconnect the connector D-24.
(3)
caution Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
Check for continuity between D-24 harness side connector terminals 40 and body earth.
OK: Continuity (Less than 2 Ω)

Q. Is the check results normal?
Then go to Step 4.
Repair the wiring harness between SRS-ECU connector D-24 terminals 40 and the body earth. Then go to Step 6.

STEP 4. Voltage measurement at the SRS-ECU connector D-24.
(1)Disconnect the negative battery terminal.
(2)Disconnect SRS-ECU connector D-24.
(3)Connect the negative battery terminal.
(4)Turn the ignition switch to the "ON" position.
(5)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Voltage measurement between D-24 harness side connector terminal No. 23, 24 and body earth.
OK: 9 V or more.

Q. Is the check result normal?
Go to Step 6.
Go to Step 5.

STEP 5. Connector check: SRS-ECU connector D-24, junction block connector D-405.


Q. Is the check result normal?
Check the harness wires for open circuit between D-24 SRS-ECU connector terminal No.23, 24 and ignition switch, and repair if necessary.
Repair it.

STEP 6. Retest the system.

Q. Can the SRS-ECU communicate with the M.U.T.-III?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Cope with Intermittent Malfunction .
Replace the SRS-ECU (Refer to ).