B1480
DTC B1400: Driver's Air Bag Module (1st Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)
DTC B1480: Driver's Air Bag Module (2nd Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)
CAUTION:
If DTC B1400 [1st squib] or B1480 [2nd squib] is set in the combination meter, always diagnose the CAN bus lines.
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:
- Short circuit in driver's air bag module (squib) or harness
- Short circuit in the clock spring
TROUBLESHOOTING HINTS
- Improper engaged connector or defective short spring*
- Short circuit in the clock spring
- Short circuit between the driver's air bag module (squib) circuit terminals
- Damaged connector(s)
- Malfunction of the SRS-ECU
NOTE:
*: The squib circuit connectors integrate a "short" spring (which prevents the air bag from deploying unintentionally due to static electricity by shorting the positive wire to the ground wire in the squib circuit when the connectors are disconnected) (Refer to General Description).
Therefore, if connector C-123, C-305 or C-307 is damaged or improperly engaged, the short spring may not be released when the connector is connected.
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.
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 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 "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. Using scan tool MB991958, read the diagnostic trouble code.
(1)Turn the ignition switch to the "ON" position.
(2)Check if the DTC is set.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is DTC B1519 set?
YES Go to Step 4.
NO Go to Step 5.
STEP 4. Check SRS-ECU connector C-123.
Q. Is the connector correctly engaged?
YES Go to Step 5.
NO Engage the connector correctly. Then go to Step 10.
STEP 5. Check SRS-ECU connector C-123, clock spring connector C-307 and driver's air bag module connector C-305. (Using scan tool MB991958, read the diagnostic trouble code.)
(1)Disconnect the negative battery terminal.
(2)Disconnect connectors C-123, C-307 and C-305, and then reconnect them.
(3)Connect the negative battery terminal.
(4)Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q. Is DTC B1400[ 1st squib] or B1480[ 2nd squib] set?
YES Go to Step 6.
NO The procedure is complete. It is assumed that DTC B1400 [1st squib] or B1480 [2nd squib] set because connector C-123, C-307 or C-305 was engaged improperly.
STEP 6. 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 clock spring side of 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 No.3 and 4 [2nd squib]) by backprobing.
(5)Connect the negative battery terminal.
(6)
CAUTION:
Always DTC B1481 is set when checking DTC B1400. 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 B1480 because the first side terminal is isolated.
Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q. Is DTC B1400[ 1st squib] or B1480[ 2nd squib] set?
YES Go to Step 7.
NO Replace the driver's air bag module (Refer to Service and Repair). Then go to Step 10.
STEP 7. 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 clock spring harness side connector C-307 (terminal No.13 and 14 [1st squib] or No.11 and 12 [2nd squib]) by backprobing.
(5)Connect the negative battery terminal.
(6)
CAUTION:
Always DTC B1481 is set when checking DTC B1400. 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 B1480 because the first side terminal is isolated.
Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q. Is DTC B1400[ 1st squib] or B1480[ 2nd squib] set?
YES Go to Step 8.
NO Replace the clock spring (Refer to Service and Repair). Then go to Step 10.
STEP 8. Check the driver's air bag module circuit. Measure the resistance at 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 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 C-123 harness side connector terminals 36 and 37 [1st squib] or 33 and 34 [2nd squib].
It should be open circuit.
Q. Does continuity exist?
YES Go to Step 9.
NO Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1400 [1st squib] or B1480 [2nd squib] set, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 10.
STEP 9. Check the harness for short circuit between SRS-ECU connector C-123 (terminal No.36 and 37 [1st squib] or No.33 and 34 [2nd squib]) and clock spring connector C-307 (terminal No.13 and 14 [1st squib] or No.11 and 12 [2nd squib]).
Q. Are harness wires between SRS-ECU connector C-123 (terminal No.36 and 37[ 1st squib] or No.33 and 34[ 2nd squib]) and clock spring connector C-307 (terminal No.13 and 14[ 1st squib] or No.11 and 12[ 2nd squib]) in good condition?
YES Go to Step 10.
NO Repair the harness wires between SRS-ECU connector C-123 and clock spring connector C-307. Then go to Step 10.
STEP 10. 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 B1400[ 1st squib] or B1480[ 2nd squib] set?
YES Return to Step 1.
NO The procedure is complete.