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DTC B1B00: Driver’s Air Bag Module (1st Squib) System (Shorted to Squib Circuit Ground)
DTC B1B04: Driver’s Air Bag Module (2nd Squib) System (Shorted to Squib Circuit Ground)








caution
  • If DTC B1B00 <1st squib> or B1B04 <2nd squib> is set in the SRS-ECU, always diagnose the CAN main bus line.
  • When DTC B1B00 is set in the following diagnosis, check the 1st squib circuit. When DTC B1B04 is set, check the 2nd squib circuit.

CIRCUIT OPERATION



DTC SET CONDITIONS


This DTC is set if there is abnormal resistance between the input terminals of the driver’s air bag module (squib).

TROUBLESHOOTING HINTS



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 ."
(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?

Go to Step 2.

Repair the CAN bus line (Refer to GROUP 54C, 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?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

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 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 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 B1B00. 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 B1B04 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?

Go to Step 4.

Replace the driver’s air bag module (Refer to ). Then go to Step 7.

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 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 harness side connector C-208 (terminal No. 3 and 4 <1st squib> or terminal No. 2 and 1 <2nd squib>) by backprobing.
(5)Connect the negative battery terminal.
(6)
caution Always DTC B1B06 is set when checking DTC B1B00. 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 B1B04 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?

Go to Step 5.

Replace the clock spring (Refer to ). Then go to Step 7.

STEP 5. Check the driver’s air bag module circuit. Measure the resistance at the SRS-ECU connector C-37.
(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)Check for continuity between C-37 harness side connector terminals 5 and 6 <1st squib> or 9 and 10 <2nd squib> and body ground.
It should be open circuit.

Q. Is it open circuit?

Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1B00 <1st squib> or B1B04 <2nd squib> sets, replace the SRS-ECU (Refer to ). Then go to Step 7.

Go to Step 6.

STEP 6. Check the harness for short circuit to ground between the following connector.



  • SRS-ECU connector C-37 (terminal No.5 and 6) and clock spring connector C-208 (terminal No.4 and 3) <1st squib>.
  • SRS-ECU connector C-37 (terminal No.9 and 10) and clock spring connector C-208 (terminal No.1 and 2) <2nd squib>.

Q. Is the check result normal?
Go to Step 7.
Repair the harness wires between SRS-ECU connector C-37 and clock spring connector C-208. Then go to Step 7.

STEP 7. 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 B1B00 <1st squib> or B1B04 <2nd squib> set?
Return to Step 1.
The procedure is complete.