Code No.B1421:
Side-airbag module (RH) (squib) system (open-circuited in the squib circuit)
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If diagnosis code B1421 is set in the combination meter,
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
- Open circuit in the side-airbag module (RH) (squib) circuit
- Improper connector contact
- Malfunction of the SRS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics.
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| warning |
Since the radiator fan rotates during CAN bus line diagnostics,
make sure that no one is servicing the engine compartment before diagnosing the CAN bus line.
Since the CAN communication stops when diagnosing the CAN bus line, the ETACS-ECU detects the
time-out of the engine-ECU, and activates the radiator fan to prevent overheating as fail-safe.
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Use the M.U.T.-III to check the CAN bus lines.
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Q.
Is the CAN bus line found to be normal?
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 Go to Step 2.
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 Repair the CAN bus lines (Refer to GROUP 54C, Troubleshooting -
Can Bus
Diagnosis Table  ).
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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)Turn the ignition switch to "ON" position.
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(3)Check if the diagnosis code is set.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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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. Check the side-airbag module (RH) (M.U.T.-III diagnosis code).
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(1)Disconnect the negative battery terminal.
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(2)Disconnect the side-airbag module harness connector C-04.
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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 resistor harness (MB991866) into the C-04 side-airbag module harness
connector (SRS-ECU side) by backprobing.
(5)Connect the negative battery terminal.
(6)Erase the diagnosis code memory, and check the diagnosis code.
Q.
Is diagnosis code B1421 set?
Go to Step 4.
Go to Step 5.
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STEP 4. Resistance measurement between the SRS-ECU connector B-109
(terminal No.12 and 13) and the side-airbag module harness connector C-04 (terminal No.2 and
1).
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(1)Disconnect SRS-ECU connector B-109 and side-airbag module harness connector C-04.
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(2)
| caution |
Do not insert a test probe into the
C-04 connector terminal from its front side directly as the connector contact pressure may be weakened.
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Resistance measurement between the following terminals.
- SRS-ECU connector B-109 (terminal No.12) and the side-airbag module harness connector
C-04 (SRS-ECU side) (terminal No.1)
- SRS-ECU connector B-109 (terminal No.13) and the side-airbag module harness connector C-04
(SRS-ECU side) (terminal No.2)
Q.
Are the check results normal?
Go to Step 6.
Repair the harness wires between SRS-ECU connector B-109 (terminal No.12 and 13)
and side-airbag module harness connector C-04 (terminal No.2 and 1).
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STEP 5. Check the side-airbag module (RH) (M.U.T.-III diagnosis code).
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(1)Disconnect the negative battery terminal.
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(2)Disconnect SRS-ECU connector B-109.
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(3)Use a flat-tipped screwdriver to pull out forward and unlock the locking button of the
side-airbag module connector (harness side), and then disconnect side-airbag module (RH) connector.
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(4)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(5)Connect special tool resistor harness (MB991884) to the C-04-1 side-airbag module
connector (harness side).
(6)Connect the negative battery terminal.
(7)Erase diagnosis code memory, and then check the diagnosis code.
Q.
Is diagnosis code B1420 set?
Replace the side-airbag module harness (RH) (Refer to ).
Replace the side-airbag module (RH) (Refer to ).
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STEP 6. Check whether the diagnosis code is reset.
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Q.
Is diagnosis code B1421 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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