B1420
DTC B1420: Side-Airbag Module (RH) (Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)
CAUTION:
If DTC B1420 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 left and right side impact sensors. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the side-airbag safing G-sensor is on, the SRS side-airbag will inflate.
- The ignition signal is input to the side-airbag module to inflate the side-airbag.
DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the side-airbag module
(RH) (squib).
TROUBLESHOOTING HINTS
- Improper engaged connector or defective short spring*
- Short between the side-airbag module (RH) (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 Description and Operation).
Therefore, if connector C-124 or D-28 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 resister
- 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 "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the check result satisfactory?
YES Go to Step 2
NO Repair the CAN bus lines 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.
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)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-124.
Q. Is the connector correctly engaged?
YES Go to Step 5.
NO Engage the connector correctly. Then go to Step 9.
STEP 5. Check SRS-ECU connector C-124 and side-airbag module (RH) connector D-28. (Using scan tool MB991958, read the diagnostic trouble code.)
(1)Disconnect the negative battery terminal.
(2)Disconnect connectors C-124 and D-28, 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 B1420 out put?
YES Go to Step 6.
NO The procedure is complete. It is assumed that DTC B1420 set because connector C-124 or D-28 was engaged improperly.
STEP 6. Check the side-airbag module (RH). (Using scan tool MB991958, read the diagnostic trouble code.)
(1)Disconnect the negative battery terminal.
(2)Disconnect the side-airbag module (RH) connector D-28.
(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 the D-28 harness side connector by backprobing.
(5)Connect the negative battery terminal.
(6)Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q. Is DTC B1420 set?
YES Go to Step 7.
NO Replace the seatback frame of the front seat (RH) Front Seat Assembly Disassembly and Assembly).
Then go to Step 9.
STEP 7. Check the side-airbag module (RH) circuit. Measure the resistance at the SRS-ECU connector C-124.
(1)Disconnect the negative battery terminal.
(2)Disconnect SRS-ECU connector C-124.
(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the side-airbag module
(RH) connector D-28 to short the squib circuit.
Disconnect side-airbag module connector D-28.
(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 57, 58 and the short spring to release the short spring.
(5)Measure at the wiring harness side.
(6)
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-124 harness side connector terminals 57 and 58.
It should be open circuit.
Q. Does continuity exist?
YES Go to Step 8.
NO Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1420 sets, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 9.
STEP 8. Check the harness wires for short circuit between SRS-ECU connector C-124 (terminal No.57 and 58) and side-airbag module (RH) connector D-28 (terminal No.1 and 2).
Q. Are the harness wires between SRS-ECU connector C-124 (terminal No.57 and 58) and side-airbag module (RH) connector D-28 (terminal No.2 and 1) in good condition?
YES Go to Step 9.
NO Repair the harness wires between SRS-ECU connector C-124 and side-airbag module
(RH) connector D-28. Then go to Step 9.
STEP 9. 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 B1420 set?
YES Return to Step 1.
NO The procedure is complete.