B1491

DTC B1411: Passenger's (Front) Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit)

DTC B1491: Passenger's (Front) Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit)

Passenger's (Front) Air Bag Module (1st Squid And 2nd Squib) Circuit:

CAUTION: If DTC B1411 [1st squib] or B1491 [2nd squib] is set in the SRS-ECU, always diagnose the CAN main bus line.

CIRCUIT OPERATION
- The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the front air bag safing G-sensor is on, the SRS air bag will inflate.
- The ignition signal is input to the air bag module to inflate the air bag.

DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the passenger's air bag module (squib).

TROUBLESHOOTING HINTS
- Open circuit in the passenger's air bag module (squib) circuit
- Improper connector contact
- 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
- MB991865: Dummy resister
- MB991866: Resister harness

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." Scan Tool Connecting
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 (Refer to Controller Area Network (CAN), Diagnosis).

STEP 2. 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 the DTC set?

YES : Go to Step 3.

NO : There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

STEP 3. Check the passenger's air bag module. (Using scan tool MB991958, read the diagnostic trouble code.)

1. Disconnect the negative battery terminal.

2. Disconnect the passenger's air bag module connector C-112.

3. Slide the outer housing of passenger's air bag module connector C-112 in the arrow direction shown, and disconnect the connector.

4. Connect special tool MB991865 to special tool MB991866.

CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

5. Insert special tool MB991866 into the harness side connector C-112 (terminal No.1 and 2 [1st squib] or terminal No.3 and 4 [2nd squib]) by backprobing.
6. Connect the negative battery terminal.
7. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC B1411 [1st squib] or B1491 [2nd squib] set?

YES : Go to Step 4.

NO : Replace the passenger's air bag module. Then go to Step 5.

STEP 4. Check the harness for open circuit between SRS-ECU connector C-123 (terminal No.27 and 28 [1st squib] or terminal No.30 and 31 [2nd squib]) and the passenger's air bag module connector C-112 (terminal No.1 and 2 [1st squib] or terminal No.4 and 3 [2nd squib]).

1. Unclip passenger's air bag module connector C-112.

2. Disconnect SRS-ECU connector C-123 and passenger's air bag module connector C-112.

CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.

3. Check for continuity between the following terminals. It should be less than 2 ohms.

[1st squib]
- SRS-ECU connector C-123 (terminal No.27) and the passenger's air bag module connector C-112 (terminal No.1)
- SRS-ECU connector C-123 (terminal No.28) and the passenger's air bag module connector C-112 (terminal No.2)

[2nd squib]
- SRS-ECU connector C-123 (terminal No.30) and the passenger's air bag module connector C-112 (terminal No.4)
- SRS-ECU connector C-123 (terminal No.31) and the passenger's air bag module connector C-112 (terminal No.3)

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1411 [1st squib] or B1491 [2nd squib] set, replace the SRS-ECU. Then go to Step 5.

NO : Replace the harness wires between SRS-ECU connector C-123 and passenger's air bag module connector C-112. Then go to Step 5.

STEP 5. Recheck for diagnostic trouble code.