Code No. B1476: IG1 power supply open circuit (Fuse No. 15 circuit)
Code No. B1477: IG1 power supply open circuit (Fuse No. 21 circuit)


caution If diagnosis code No. B1476 (fuse No. 15) or B1477 (fuse No. 21) is set in the SRS-ECU, be sure to diagnose the CAN bus line.

OPERATION
SRS-ECU has two independent battery power supplies circuit (fuse Nos. 15 and 21) having fuses.

TROUBLE JUDGEMENT
The code is set when the voltage between the IG1 terminal (SRS-ECU terminal IG1A or No. IG1B) and the earth drops below the specified value for 5 seconds continuously. Also, if the diagnosis code Nos. B1476 and B1477 are set at the same time, the battery voltage may have dropped. Therefore, check the battery first.

PROBABLE CAUSES

  • Open circuit to power supply circuit
  • Damaged wiring harness and connectors
  • Malfunction of SRS-ECU
  • Malfunction of ETACS-ECU

DIAGNOSIS PROCEDURE

STEP 1. Power supply fuse 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 "LOCK" (OFF).
(3)Check the fuse.

Q. Is the fuse in good condition?
Go to Step 3.
Repair the wiring harness IG1A line between the junction block connector and the SRS-ECU connector <fuse No. 15>, IG1B line between the junction block connector and the SRS-ECU connector <fuse No. 21> and replace the power supply fuse.

STEP 3. M.U.T.-III CAN bus diagnostics.
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 4.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ). Then go to Step 4.

STEP 4. M.U.T.-III other system diagnosis code.
Check if the ETACS diagnosis code is set.

Q. Is the diagnosis code set?
Diagnose the ETACS.
Check the input signal of ETACS-ECU ignition switch (IG1). Then go to Step 5.

STEP 5. Check whether the diagnosis code is set again.
(1)Connect the negative battery terminal.
(2)After erasing the diagnosis code memory, check the diagnosis code again.
(3)Disconnect the negative battery terminal.

Q. Is diagnosis code No. B1476 or B1477 set?
Go to Step 6.
Intermittent malfunction.

STEP 6. Resistance measurement at the SRS-ECU connector.
(1)Disconnect the SRS-ECU connectors.
(2)Take the measurements below at the wiring harness side connectors.

  • Continuity GND1 line between wiring harness side connector and body earth
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?
Go to Step 7.
Repair the wiring harness GND1 line between the SRS-ECU connector and the body earth.

STEP 7. Voltage measurement at the SRS-ECU connector (IG1A, IG1B line).
(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 harness side connector.

  • Voltage IG1A, IG1B line between SRS-ECU connector and body earth
OK: 9 V or more
(6)Disconnect the negative battery terminal.

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

STEP 8. 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 junction block connector.
(3)Disconnect the SRS-ECU connector.
(4)
  • Continuity IG1A line between junction block connector and SRS-ECU connector
  • Continuity IG1B line between junction block connector and SRS-ECU connector
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?
Replace the ETACS-ECU.
Repair the wiring harness IG1A line between the junction block connector and the SRS-ECU connector, IG1B line between the junction block connector and the SRS-ECU connector.

STEP 9. Check whether the diagnosis code is set again.

Q. Is diagnosis code No. B1476 or B1477 set?
Replace SRS-ECU.
Intermittent malfunction.