B1493

DTC B1413: Passenger's
(Front) Air Bag Module (1st Squib) System Fault for Power Supply Circuit (Short-Circuited to Power Supply)
DTC B1493: Passenger's (Front) Air Bag Module (2nd Squib) System Fault for Power Supply Circuit (Short-Circuited to Power Supply)

CAUTION:
If DTC B1413 [1st squib] or B1493 [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

- Damaged harness wires and connectors
- Short to the power supply in the passenger's air bag module (squib) harness
- 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 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.
(5)
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 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)
CAUTION:
Always DTC B1491 is set when checking DTC B1413. This is because the second side terminal is isolated when checking it, DTC B1493 is set but this is not a fault. In addition, always DTC B1411 is set when checking DTC B1490 because the first side terminal is isolated.

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

Q. Is DTC B1413[ 1st squib] B1493[ 2nd squib] set?

YES Go to Step 4.

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

STEP 4. Check the passenger's air bag module circuit. Measure the voltage at the SRS-ECU connector C-123.

(1)Disconnect the negative battery terminal.

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

(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the passenger's air bag module connector C-112 to short the squib circuit.

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

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

(5)
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 27 and 28 [1st squib] or 30 and 31 [2nd squib], and the short spring to release the short spring.
(6)Connect the negative battery terminal.
(7)Turn the ignition switch to the "ON" position.

(8)
CAUTION:
Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Measure the voltage between C-123 harness side connector terminals 27 and 28 [1st squib] or 30 and 31 [2nd squib] and body ground.
Voltage should measure 0 volt.

Q. Is the measured voltage 0 volt?

YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1413 [1st squib] B1493 [2nd squib] sets, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 6.

NO Go to Step 5.

STEP 5. Check the harness wires for short circuit to power supply between SRS-ECU connector C-123 (terminal No.27 and 28 [1st squib] or terminal No.30 and 31 [2nd squib]) and passenger's air bag module connector C-112 (terminal No.1 and 2 [1st squib] terminal No.4 and 3 [2nd squib]).

Q. Are the harness wires between SRS-ECU connector C-123 (terminal No.27 and 28[ 1st squib] or terminal No.30 and 31[ 2nd squib]) and passenger's air bag module connector C-112 (terminal No.1 and 2[ 1st squib] terminal No.4 and 3[ 2nd squib]) in good condition?

YES Go to Step 6.

NO Repair the harness wires between SRS-ECU connector C-123 and passenger's air bag module connector C-112. Then go to Step 6.

STEP 6. Recheck for diagnostic trouble code.