Code No.B1476: Power Supply Voltage (Ig1 (A) Voltage) Drops Abnormally. (Fuse No.2 Circuit)
Code No.B1477: Power Supply Voltage (Ig1 (B) Voltage) Drops Abnormally. (Fuse No.3 Circuit)




















caution If diagnosis code B1476 Fuse No.2 or B1477 Fuse No.3 is set in the SRS-ECU always diagnose the CAN bus lines.

OPERATION



DIAGNOSIS CODE SET CONDITIONS


This diagnosis code is set if the voltage between the IG1 terminals (fuse No.2 circuit or fuse No.3 circuit) and earth is lower than a predetermined value for a continuous period of 5 seconds or more.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics.
Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54D, Diagnosis ).

STEP 2. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition: "LOCK" (OFF) position to "ON"
(3)On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code set?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 3. Check junction block fuse number 2 <B1476> or 3 <B1477>.

Q. Is the fuse burned out?

Go to Step 6.

Go to Step 4.

STEP 4. Check the power supply circuit for open circuit. Voltage measurement at 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.
Measure the voltage between D-24 harness side connector terminal 24 <B1476> or 23 <B1477> and body earth.
OK: 9 V or more.

Q. Is the measured voltage within the specified range?
Go to Step 10.
Go to Step 5.

STEP 5. Wiring harness check between the SRS-ECU connector D-24 and the ignition switch connector D-309.
note Prior to the wiring harness inspection, check the junction block connectors D-403 and D-405, and repair if necessary.

  • Open circuit check for the SRS-ECU power supply wire

Q. Is the check result normal?
Go to Step 10.
Repair or replace it.

STEP 6. Check a burned-out fuse.
(1)Replace the fuse.
(2)Turn the ignition switch to the "ON" position, wait for at least one minute and then the ignition switch to the "LOCK" (OFF) position.
(3)Check the fuse.

Q. Is the fuse in good condition?
The procedure is complete.
Go to Step 7.

STEP 7. Check the SRS-ECU power supply circuit for short circuit to earth. Resistance measurement at the junction block connector D-405.
(1)Disconnect junction block connector D-405, and measure at the wiring harness side.
(2)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Measure the resistance between terminal 24 <B1476> or 7 <B1477> and body earth.
OK: Open circuit

Q. Is the check result normal?
Go to Step 8.
Go to Step 9.

STEP 8. Check the SRS-ECU power supply circuit for short circuit to earth. Resistance measurement at the junction block connector D-405.
(1)Disconnect junction block connector D-405, and measure at the wiring harness side.
(2)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Measure the resistance between terminal 25 and body earth.
OK: Open circuit

Q. Is the check result normal?
Check the other circuit, which flows through fuse No.2.
Repair the harness wires between junction block connector D-405 (terminal No.25) and combination meter connector D-02 (terminal No.42).

STEP 9. Check the power supply circuit for short circuit to earth. Resistance measurement at the SRS-ECU connector D-24.
(1)Disconnect SRS-ECU connector D-24, and measure at the wiring harness side.
(2)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Measure the resistance between terminal 24 <B1476> or 23 <B1477> and body earth.
OK: Open circuit

Q. Is the check result normal?
Go to Step 10.
Repair the wiring harness between SRS-ECU connector D-24 (terminal No.24 and 23) and junction block connector D-405 (terminal No.24 and 7).

STEP 10. Check whether the diagnosis code is reset.

Q. Is diagnosis code B1476 or B1477 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).