B1476

DTC B1476: Open Circuit to IG1 Power Supply (Fuse No.12 Circuit)
DTC B1477: Open Circuit to IG1 Power Supply (Fuse No.18 Circuit)

CAUTION:
If DTC B1476 (Fuse No.12) or B1477 (Fuse No.18) is set in the SRS-ECU, always diagnose the CAN main bus lines.

CIRCUIT OPERATION

- The SRS-ECU is powered from the fusible link (34).
- The SRS-ECU power is supplied from two circuits. Even if one circuit is shut off, the air bag can inflate.

DTC SET CONDITIONS

This code is set when an open circuit occurs in the power supply circuit to the SRS-ECU
(terminal No.61) or in the power supply circuit to the SRS-ECU (terminal No.62). Also, if the code No. B1476 and B1477 are set at the same time, the battery voltage may have dropped. Therefore, check the battery first.

TROUBLESHOOTING HINTS

- Open circuit to power supply circuit
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
- Malfunction of ETACS-ECU

DIAGNOSIS

STEP 1. Power supply fuse number 12,18 check.

Q. Is the fuse in good condition?

YES Go to Step 3.
NO Go to Step 2
STEP 2. Check for a blown fuse.

(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?

YES Go to Step 3.
NO Repair the wiring harness between the C-313 ETACS-ECU connector terminal No. 4/2 and the C-27 SRS-ECU connector terminal No. 61/62, and replace the power supply fuse.
STEP 3. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."

(2)Turn the ignition switch to the "ON" position.

(3)Diagnose the CAN bus line.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 4.
NO Repair the CAN bus line CAN Bus Diagnostics Chart).
STEP 4. Using scan tool MB991958, diagnose the ETACS.

CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."

(2)Turn the ignition switch to the "ON" position.

(3)Check if the DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Diagnose the ETACS, Electronic Time and Alarm Control System (ETACS).
NO Check the input signal of ETACS-ECU ignition switch (IG1) Inspection Procedure 2). Than go to step 5.
STEP 5. Recheck for diagnostic trouble code.

Check again if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to "ON" position.

(3)Check if the DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Go to Step 6.
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).
STEP 6. Resistance measurement at the C-126 SRS-ECU connector.

(1)While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-126 SRS-ECU connector.

(2)Take the measurements below at the C-126 wiring harness side connectors. It should be less than 2 ohms.

- Continuity between C-126 wiring harness side connector terminal No. 24 and body ground

Q. Does continuity exist?

YES Go to Step 7.

NO Repair the wiring harness between the C-126 SRS-ECU connector terminal No. 24 and the ground.

STEP 7. Measure the voltage at the C-126 SRS-ECU connector.

(1)Disconnect the negative battery terminal.

(2)While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-126 SRS-ECU connector.
(3)Connect the negative battery terminal.
(4)Ignition switch: ON

(5)Take the measurements below at the C-126 harness side connector.

- Voltage between terminal No. 21/22 and body ground
OK: 9 V or more

Q. Is the measured voltage within the specified range?

YES Go to Step 9.

NO Go to Step 8.

STEP 8. Check the harness for open circuit between SRS-ECU connector C-126 terminal No.21 and the ETACS-ECU connector C-412 terminal No.4 or between SRS-ECU connector C-126 terminal No.22 and the ETACS-ECU connector C-417 terminal No.5.

(1)Disconnect the negative battery terminal.

(4)Check for continuity between the following terminals. It should be less than 2 ohms.
[Fuse No.12]

- SRS-ECU connector C-126 (terminal No.22) and the ETACS-ECU connector C-417 (terminal No.5)
[Fuse No.18]

- SRS-ECU connector C-126 (terminal No.21) and the ETACS-ECU connector C-412 (terminal No.4)

Q. Does continuity exist?

YES Replace the ETACS-ECU Electronic Time and Alarm Control System (ETACS)-ECU Removal and Installation).

NO Repair the harness wire between SRS-ECU connector C-126 and the ETACS-ECU connector C-412 or C-417.

STEP 9. Recheck for diagnostic trouble code.

Check again if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to the "ON" position.

(3)Check if the DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC B1476 [Fuse No.12 circuit] or B1477 [Fuse No.18 circuit] set?

YES Replace the SRS-ECU (Refer to Service and Repair).
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).