B1481

DTC B1401: Driver's Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit)
DTC B1481: Driver's Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit)

CAUTION:
If DTC B1401 [1st squib] or B1481 [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 via the clock spring to inflate the air bag.

DTC SET CONDITIONS

- This DTC is set if there is abnormal resistance between the input terminals of the driver's side air bag module (squib). The most likely causes for this code to be set are the followings:
- Open circuit in the driver's air bag module (squib) or harness
- Open circuit in the clock spring
- Malfunction of connector contact

TROUBLESHOOTING HINTS

- Open circuit in the clock spring
- Open circuit due to improper neutral position of the clock spring
- Open circuit in the driver's air bag module (squib) circuit
- Disengaged driver's air bag module (squib) connector
- 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 resistor
- MB991866: Resister harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

(1)
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.

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 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 How to Cope With Intermittent Malfunctions).

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

(1)Disconnect the negative battery terminal.

(2)Slide the outer housing of the driver' s air bag module connector C-305 in the arrow direction shown, and disconnect the connector.

(3)Connect special tool MB991865 to special tool MB991866.
(4)
CAUTION:
Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Insert special tool MB991866 into clock spring side of driver's air bag module connector C-305 (terminal No.1 and 2 [1st squib] or terminal No.3 and 4 [2nd squib]) by backprobing.
(5)Connect the negative battery terminal.
(6)
CAUTION:
Always DTC B1481 is set when checking DTC B1401. This is because the second side terminal is isolated when checking it, DTC B1481 is set but this is not a fault. In addition, always DTC B1401 is set when checking DTC B1481 because the first side terminal is isolated.

Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q. Is DTC B1401[ 1st squib] or B1481[ 2nd squib] set?

YES Go to Step 4.

NO Replace the driver's air bag module (Refer to Service and Repair).
Then go to Step 6.

STEP 4. Check the clock spring. (Using scan tool MB991958, read the diagnostic trouble code.)

(1)Disconnect the negative battery terminal.

(2)Disconnect the clock spring connector C-307.

(3)Connect special tool MB991865 to special tool MB991866.
(4)
CAUTION:
Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Insert special tool MB991866 into harness side of clock spring connector C-307 (terminal No.13 and 14 [1st squib] or terminal No.11 and 12 [2nd squib]) by backprobing.
(5)Connect the negative battery terminal.
(6)
CAUTION:
Always DTC B1481 is set when checking DTC B1401. This is because the second side terminal is isolated when checking it, DTC B1481 is set but this is not a fault. In addition, always DTC B1401 is set when checking DTC B1481 because the first side terminal is isolated.

Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q. Is DTC B1401[ 1st squib] or B1481[ 2nd squib] set?

YES Go to Step 5.

NO Replace the clock spring (Refer to Service and Repair). Then go to Step 6.

STEP 5. Check the harness between the SRS-ECU connector C-123 (terminal No.11 and 12) and the clock spring connector C-307 (terminal No.3 and 4) for open circuit.

(1)Disconnect the negative battery terminal.

(2)Disconnect SRS-ECU connector C-123.

(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect clock spring connector C-307 to short the squib circuit.

Disconnect clock spring connector C-307.

(4)
CAUTION:
Insert an insulator such as a cable tie to a depth of 4mm (0.16 inch) or more, otherwise the short spring will not be released.

Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 36, 37 [1st squib] or 33, 34 [2nd squib] and the short spring to release the short spring.

(5)
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 following terminals. It should be less than 2 ohms.
[1st squib]

- SRS-ECU connector C-123 (terminal No.36) and the clock spring connector C-307 (terminal No.13)
- SRS-ECU connector C-123 (terminal No.37) and the clock spring connector C-307 (terminal No.14)
[2nd squib]

- SRS-ECU connector C-123 (terminal No.33) and the clock spring connector C-307 (terminal No.11)
- SRS-ECU connector C-123 (terminal No.34) and the clock spring connector C-307 (terminal No.12)

Q. Does continuity exist?

YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1401 [1st squib] or B1481 [2nd squib] set, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 6.

NO Repair the harness wires between SRS-ECU connector C-123 and clock spring connector C-307. Then go to Step 6.

STEP 6. Recheck for diagnostic trouble code.