B1476
DTC B1476: IG1 Power Supply Circuit System (Fuse No.3 Circuit)
DTC B1477: IG1 Power Supply Circuit System (Fuse No.2 Circuit)
CAUTION:
If DTC B1476 [Fuse No.3] or B1477 [Fuse No.2] is set in the combination meter, always diagnose the CAN bus lines.
CIRCUIT OPERATION
- The SRS-ECU is powered from the ignition switch (IG1).
- 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 DTC is set if the voltage between the IG1 terminals (fuse No.3 circuit or fuse No.2 circuit) and ground is lower than a predetermined value for a continuous period of five second or more. However, if the vehicle condition returns to normal, DTC number B1476 [Fuse No.3] or B1477 [Fuse No.2] will be automatically erased, and the SRS warning light will switch off.
TROUBLESHOOTING HINTS
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
STEP 1. 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 2.
NO Repair the CAN bus line CAN Bus Diagnostics Chart).
STEP 2. 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 3.
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).
STEP 3. Check junction block fuse number 3 [DTC B1476] or 2 [DTC B1477].
Q. Is the fuse burned out?
YES Go to Step 6.
NO Go to Step 4.
STEP 4. Check the power supply circuit for open circuit. Measure the voltage at SRS-ECU connector C-123.
(1)Disconnect the negative battery terminal.
(2)Disconnect SRS-ECU connector C-123.
(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 C-123 harness side connector terminal 23 [DTC B1476] or 24 [DTC B1477] and body ground.
Voltage should measure 9 volts or more.
Q. Is the measured voltage 9 volts or more?
YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1476 or B1477 set, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 9.
NO Go to Step 5.
STEP 5. Check the harness for open circuit between SRS-ECU connector C-123 (terminal No.23 [DTC B1476] or terminal No.24 [DTC B1477]) and the ignition switch (Ig1).
NOTE:
After inspecting intermediate connectors C-202 and C-215, inspect the wiring harness. If intermediate connectors are damaged, repair or replace them. Harness Connector Inspection. Then go to Step 10.
Q. Is the harness wire between SRS-ECU connector C-123 (terminal No.23[ DTC B1476] or terminal No.24[ DTC B1477]) and the ignition switch (Ig1) in good condition?
YES Go to Step 9.
NO Repair the harness wire between SRS-ECU connector C-123 and the ignition switch connector (Ig1). Then go to Step 9.
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 turn the ignition switch to the "LOCK" (OFF) position.
(3)Check the fuse.
Q. Is the fuse in good condition?
YES Go to Step 9.
NO It is possible that the circuit using fuse No.3 [DTC B1476] or No.2 [DTC B1477] is shorted, go to Step 7.
STEP 7. Check the SRS-ECU power supply circuit for short circuit to ground. Measure the resistance at the junction block connector C-215.
(1)Disconnect junction block connector C-215, and measure at the wiring harness side.
(2)Disconnect SRS-ECU connector C-123.
(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 terminal 7 [DTC B1476] or 24 [DTC B1477] and body ground.
It should be open circuit.
Q. Does continuity exist?
YES Repair the harness wire between SRS-ECU connector C-123 and junction block connector C-215. Then go to Step 9.
NO Go to Step 8.
STEP 8. Check the power supply circuit for open circuit to ground. Measure the resistance at the SRS-ECU connector C-123.
(1)Disconnect junction block connector C-215.
(2)
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 the harness side connector terminal No. 23 [DTC B1476] or No. 24 [DTC B1477] and body ground with the SRS-ECU side connector connected.
It should be open circuit.
Q. Does continuity exist?
YES Replace the SRS-ECU.
NO Go to Step 9.
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 or DTC B1477 set?
YES Return to Step 1.
NO The procedure is complete.