Code No.B1420: Side-airbag squib (RH) short-circuited
| caution |
If diagnosis code B1420 is set in the SRS-ECU, always
diagnose the CAN bus lines.
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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.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if there
is abnormal resistance between the input terminals of the side-airbag module
(RH) (squib).
PROBABLE CAUSES
- Improper engaged connector or defective short spring*
- Short circuit 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 earth wire
in the squib circuit when the connectors are disconnected). Therefore, if
connector D-23, E-123 or E-127 is damaged or improperly engaged, the short
spring may not be released when the connector is connected.
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use the M.U.T.-III to diagnose the CAN bus
lines.
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Q.
Is the check result normal?
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 Go to Step 2
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 Repair
the CAN bus lines (Refer to GROUP 54D, Diagnosis ).
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STEP 2. Check whether the diagnosis code is reset.
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Check again if the diagnosis code is
set.
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(1)Erase the diagnosis code.
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(2)Ignition: "LOCK" (OFF) position to "ON"
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(3)On completion, check that the diagnosis code is not
reset.
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Q.
Is the diagnosis code set?
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Go to Step 3.
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There
is an intermittent malfunction such as poor engaged connector(s) or open
circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
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STEP 3. M.U.T.-III diagnosis code.
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| caution |
To prevent damage to M.U.T.-III MB991958, always
turn the ignition switch to the "LOCK" (OFF) position before connecting
or disconnecting M.U.T.-III MB991958.
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(1)Turn the ignition switch to the "ON" position.
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(2)Check if the diagnosis code is set.
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(3)Turn the ignition switch to the "LOOK" (OFF)
position.
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Q.
Is diagnosis code B1519 set?
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Go to Step 4.
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Go to Step 5.
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STEP 4. Connector check: SRS-ECU connector D-23.
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Q.
Is the connector correctly engaged?
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Go to Step 5.
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Engage
the connector correctly. The procedure is complete.
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STEP 5. Connector lock check: SRS-ECU connector D-23, intermediate
connector E-123 and side-airbag module (RH) connector E-127.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect connectors D-23, E-123 and E-127, and then
reconnect them.
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(3)Connect the negative battery terminal.
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(4)Erase the diagnosis code from memory, and check the
diagnosis code.
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Q.
Is diagnosis code B1420 set?
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Go to Step 6.
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The
procedure is complete. It is assumed that diagnosis code B1420 set because
connector D-23, E-123 or E-127 was engaged improperly.
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STEP 6. Check the side-airbag module (RH).
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(1)Disconnect the negative battery terminal.
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(2)Disconnect the side-airbag module (RH) connector
E-127.
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(3)Connect special tool dummy resistor
(MB991865) to special tool resistor harness (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.
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Insert special tool MB991866 into the E-127 harness side connector
by backprobing.
(5)Connect the negative battery terminal.
(6)Erase
the diagnosis code from memory, and check the diagnosis code.
Q.
Is diagnosis code B1420 set?
Go to Step 7.
Replace the seatback frame of the
front seat (RH) (Refer to GROUP 52A, Front Seat ).
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STEP 7. Check the side-airbag module (RH) circuit. Resistance
measurement at the SRS-ECU connector D-23.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect SRS-ECU connector D-23.
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(3)
| danger |
To prevent the air bag from deploying
unintentionally, disconnect the side-airbag module (RH) connector E-127
to short the squib circuit.
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Disconnect side-airbag module (RH) connector E-127.
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(4)
| caution |
Insert an insulator such as a cable tie to a depth
of 4 mm or more, otherwise the short spring will not be
released.
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Insert a cable tie [3 mm wide, 0.5 mm thick] between
terminals 57, 58 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.
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Check for continuity between D-23 harness side connector terminals
57 and 58.
OK: Open circuit
Q.
Is the check result normal?
Go to Step 8.
Repair the harness wires between
SRS-ECU connector D-23 (terminal No.57 and 58) and side-airbag module (RH)
connector E-127 (terminal No.1 and 2).
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STEP 8. Check whether the diagnosis code is reset.
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Q.
Is diagnosis code B1420 set?
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Replace the SRS-ECU (Refer to ).
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An
intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with
Intermittent Malfunction ).
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