B1477
This document has been updated per Mitsubishi TSB# 06-52b-001DTC B1476: IG1 Power Supply Circuit System (Fuse No.3 Circuit)
DTC B1477: IG1 Power Supply Circuit System (Fuse No.2 Circuit)
IG1 Power Supply Circuit:
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.2 circuit or fuse No.3 circuit) and ground is lower than a predetermined value for a continuous period of five second or more.
TROUBLESHOOTING HINTS
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: MUT-III USB Cable
- MB991910: MUT-III Main Harness A
- MB991223 (MB991222): Harness set (Probe)
STEP 1. Check junction block fuse number 3 (DTC B1476) or 2 (DTC B1477).
Q: Is the fuse burned out?
YES: Go to Step 4.
NO: Go to Step 2.
STEP 2. Check the power supply circuit for open circuit at the SRS-ECU connector C-28.
1. Disconnect the negative battery terminal.
2. Disconnect SRS-ECU connector C-28.
3. Connect the negative battery terminal.
4. Turn the ignition switch to the "ON" position.
CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
5. Measure the voltage between C-28 harness 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 sets, replace the SRS-ECU. Then go to Step 10.
NO: Go to Step 3.
STEP 3. Check the harness for open circuit between SRS-ECU connector C-28 {terminal No.23 (DTC B1476) or 24 (DTC B1477)} and the ignition switch connector C-208 (terminal No.2).
NOTE: After inspecting intermediate connectors C-214 and C-211, inspect the wiring harness. If intermediate connectors are damaged, repair or replace them.
Q: Is harness between SRS-ECU connector C-28 {terminal No.23 (DTC B1476) or 24 (DTC B1477)} and the ignition switch connector C-208 (terminal No.2) in good condition?
YES: Go to Step 10.
NO: Repair the harness wire between SRS-ECU connector C-28 and the ignition switch connector C-208. Then go to Step 10.
STEP 4. 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 10.
NO: Go to Step 5.
STEP 5. Check the SRS-ECU power supply circuit for short circuit to ground at the junction block connector C-214.
1. Disconnect junction block connector C-214, and measure at the wiring harness side.
CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
2. 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: Go to Step 8.
NO: Go to Step 6.
STEP 6. Check the fuse number 2-related circuit at junction block connector C-214.
1. Disconnect junction block connector C-214, and measure at the wiring harness side.
CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
2. Check for continuity between C-214 harness connector terminal 25 and body ground.
It should be open circuit.
Q: Does continuity exist?
YES: Go to Step 7.
NO: Check the other circuit, which flows through multi-purpose fuse number 2.
STEP 7. Check the harness for short circuit to ground between junction block connector C-214 (terminal No.25) and combination meter connector C-01 (terminal No.9).
NOTE: After inspecting intermediate connector C-21, inspect the wiring harness. If intermediate connectors are damaged,repair or replace them.
Q: Is the harness wire between junction block connector C-214 (terminal No.25) and combination meter connector C-01 (terminal No.9) in good condition?
YES: Go to Step 10.
NO: Repair the harness wire between junction block connector C-214 and combination meter connector C-01. Then go to Step 10.
STEP 8. Check the power supply circuit for short circuit to ground at the SRS-ECU connector C-28.
1. Disconnect SRS-ECU connector C-28, and measure at the wiring harness side.
CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
2. Check for continuity between terminal No.23 (DTC B1476) or 24 (DTC B1477) and body ground.
It should be open circuit.
Q: Is the circuit normal?
YES: Go to Step 9.
NO: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1476 or B1477 sets, replace the SRS-ECU. Then go to Step 10.
STEP 9. Check the harness for short circuit to ground between SRS-ECU connector C-28 {terminal No.23 (DTC B1476) or 24 (DTC B1477)} and junction block connector C-214 {terminal 7 (DTC B1476) or 24 (DTC B1477)}.
Q: Are harness wire between SRS-ECU connector C-28 {terminal No.23 (DTC B1476) or 24 (DTC B1477)} and junction block connector C-214 {terminal 7 (DTC B1476) or 24 (DTC B1477)} in good condition?
YES: Go to Step 10.
NO: Repair the harness wires between SRS-ECU connector C-28 and junction block connector C-214. Then go to Step 10.
STEP 10. 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 B1477 set?
YES: Return to Step 1.
NO: The procedure is complete.