Code No.B1420:
Side-Airbag Module (RH) (Squib) System Fault 1 (Short Circuit
between Terminals of the Squib
Circuit)
| caution |
If diagnosis code B1420 is set in the
SRS-ECU, always diagnose
the CAN bus lines.
|
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 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). (Refer to  ).
Therefore, if connector C-118 or D-29 is damaged or
improperly engaged, the short spring may
not be released when the connector is connected.
|
|
|
STEP 1. M.U.T.-III CAN bus diagnostics
|
|
|
Use the M.U.T.-III to diagnose the
CAN bus lines.
|
|
|
Q.
Is the check result normal?
|
|
|
 Go to Step
2
|
|
|
|
|
|
 Repair the CAN bus
lines (Refer to GROUP 54F, Diagnosis ).
|
|
|
|
|
|
STEP 2. Check whether the diagnosis code is
reset.
|
|
|
Check again if the diagnosis code
is set.
|
|
|
(1)Erase the diagnosis code.
|
|
|
(2)Ignition: LOCK (OFF) position to ON
|
|
|
(3)On completion, check that the diagnosis code is
not reset.
|
|
|
Q.
Is the diagnosis code 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. M.U.T.-III diagnosis code
|
|
|
| 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.
|
|
|
|
(1)Turn the ignition switch to the "ON"
position.
|
|
|
(2)Check if the diagnosis code is set.
|
|
|
(3)Turn the ignition switch to the "LOOK (OFF)"
position.
|
|
|
Q.
Is diagnosis code B1519 set?
|
|
|
Go to Step
4.
|
|
|
|
|
|
Go to Step
5.
|
|
|
|
|
|
STEP 4. Connector lock check: SRS-ECU connector C-118
(M.U.T.-III diagnosis
code).
|
|
|
(1)Disconnect the negative battery
terminal.
|
|
(2)Disconnect connectors C-118 and
then reconnect them.
(3)Connect the negative battery
terminal.
(4)Erase the diagnosis code memory, and check
the diagnosis code.
Q.
Is diagnosis code B1420 out put?
Go to Step
5.
The
procedure is complete. It is assumed that diagnosis code
B1420 set as connector
C-118 was engaged improperly.
|
|
|
STEP 5. Connector lock check: SRS-ECU connector C-118
and side-airbag
module (RH) connector D-29 (M.U.T.-III diagnosis
code).
|
|
|
(1)Disconnect the negative battery
terminal.
|
|
(2)Disconnect connectors C-118 and
D-29, and then reconnect them.
(3)Connect the negative
battery terminal.
(4)Erase the diagnosis code memory, and
check the diagnosis code.
Q.
Is diagnosis code B1420 out put?
Go to Step
6.
The
procedure is complete. It is assumed that diagnosis code
B1420 set because
connector C-118 or D-29 was engaged improperly.
|
|
|
STEP 6. Check the side-airbag module (RH) (M.U.T.-III
diagnosis code).
|
|
|
(1)Disconnect the negative battery
terminal.
|
|
(2)Disconnect the side-airbag
module (RH) connector D-29.
|
|
(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.
|
Insert special tool MB991866 into the D-29 harness
side connector by backprobing.
(5)Connect the negative
battery terminal.
(6)Erase the diagnosis code memory, and
check the diagnosis code.
Q.
Is diagnosis code B1420 set?
Go to Step
7.
Replace
the frame assembly of the front seat (RH) (Refer to GROUP
52A, Front Seat ).
|
|
|
STEP 7. Check the side-airbag module (RH) circuit.
Resistance measurement
at the SRS-ECU connector C-118.
|
|
(1)Disconnect SRS-ECU connector
C-118.
|
|
(2)
| danger |
To prevent the air bag from
deploying unintentionally, disconnect the
side-airbag module
(RH) connector D-29 to short the squib
circuit.
|
Disconnect side-airbag module connector
D-29.
|
|
(3)
| caution |
Insert an insulator such as a
cable tie to a depth of 4mm or more, otherwise
the short
spring will not be released.
|
Insert a cable tie [3 mm wide, 0.5 mm
thick]
between terminals 57, 58
and the short spring to release the short
spring.
(4)Measure at the wiring harness side.
|
|
(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-118 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 C-118 (terminal
No.57 and 58)
and side-airbag module (RH) connector D-29 (terminal No.1
and 2).
|
|
|
STEP 8. Check whether the diagnosis code is
reset.
|
|
|
Q.
Is diagnosis code B1420 set?
|
|
|
Replace the SRS-ECU
(Refer to ).
|
|
|
|
|
|
An intermittent
malfunction is suspected (Refer to GROUP 00, How to Use
Troubleshooting/Inspection Service
Points ).
|
|
|
|