B1B02

DTC B1B02: Driver's Air Bag Module (1st squib) System (Squib Circuit Open)
DTC B1B06: Driver's Air Bag Module (2nd squib) System (Squib Circuit Open)













CAUTION:

- If DTC B1B02[ 1st squib] or B1B06[ 2nd squib] is set in the SRS-ECU, always diagnose the CAN main bus line.
- When DTC B1B02 is set in the following diagnosis, check the 1st squib circuit. When DTC B1B06 is set, check the 2nd squib circuit.

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 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: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN Communication System)
- 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.

(1)Disconnect the negative battery terminal.





(2)Slide the outer housing of the driver' s air bag module connector C-204 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-204 (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 B1B06 is set when checking DTC B1B02. This is because the second side terminal is isolated when checking it. DTC B1B06 is set but this is not a fault. In addition, always DTC B1B02 is set when checking DTC B1B06 because the first side terminal is isolated.

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

Q. Is the checked DTC set?

YES Go to Step 4.

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

STEP 4. Check the clock spring.

(1)Disconnect the negative battery terminal.

(2)Disconnect the clock spring connector C-208.





(3)Connect special tool MB991865 to special tool MB991866.
(4)
CAUTION:
Do not insert a 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-208 (terminal No.3 and 4 [1st squib] or terminal No.1 and 2 [2nd squib]) by backprobing.
(5)Connect the negative battery terminal.
(6)
CAUTION:
Always DTC B1B06 is set when checking DTC B1B02. This is because the second side terminal is isolated when checking it. DTC B1B06 is set but this is not a fault. In addition, always DTC B1B02 is set when checking DTC B1B06 because the first side terminal is isolated.

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

Q. Is the checked DTC set?

YES Go to Step 5.

NO Replace the clock spring (Refer to Removal and Installation). Then go to Step 6.

STEP 5. Check the harness for open circuit between the SRS-ECU connector C-37 and the clock spring connector C-208.

(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-37 SRS-ECU connector.
(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the clock spring connector C-208 to short the squib circuit.

Disconnect the clock spring connector C-208.









(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 5, 6 [1st squib] or 9, 10 [2nd squib] and the short spring to release the short spring.









(5)
CAUTION:
Do not insert a probe into the terminal from C-208 harness side connector 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.

- SRS-ECU connector C-37 (terminal No.5) and the clock spring connector C-208 (terminal No.4)[ 1st squib]
- SRS-ECU connector C-37 (terminal No.6) and the clock spring connector C-208 (terminal No.3)[ 1st squib]

- SRS-ECU connector C-37 (terminal No.9) and the clock spring connector C-208 (terminal No.1)[ 2nd squib]
- SRS-ECU connector C-37 (terminal No.10) and the clock spring connector C-208 (terminal No.2)[ 2nd squib]

Q. Does continuity exist?

YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTCB1B02 [1st squib] or B1B06 [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-37 and clock spring connector C-208. Then go to Step 6.

STEP 6. 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 DTCB1B02[ 1st squib] or B1B06[ 2nd squib] set?

YES Return to Step 1.
NO The procedure is complete.