Code No.B1470: Seat Belt Pre-Tensioner (LH) (Squib) System Fault 1 (Short
Circuit between Terminals of the Squib Circuit)
caution |
If diagnosis code B1470 is set in the SRS-ECU, always
diagnose the CAN main bus line.
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OPERATION
The SRS-ECU judges how severe a collision is by
detecting signals from the front impact sensors and the front air bag analogue
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
pre-tensioner will deploy.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if there
is abnormal resistance between the input terminals of the seat belt
pre-tensioner (LH) (squib).
PROBABLE CAUSES
- Improper engaged connector or defective short spring*
- Short circuit between the seat belt pre-tensioner (LH) (squib) circuit
terminals
- Damaged connector(s)
- Malfunction of the SRS-ECU
note |
*: The squib circuit connectors integrate a
"short" spring (which prevents the seat belt pre-tensioner 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-25 or E-16 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 line (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-25.
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Q.
Is the connector correctly engaged?
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Go to Step 5.
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Engage
code from memory the connector correctly. The procedure is
complete.
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STEP 5. Connector lock check: SRS-ECU connector D-25 and seat belt
pre-tensioner (LH) connector E-16.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect connectors D-25 and E-16, 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 B1470 set?
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Go to Step 6.
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The
procedure is complete. It is assumed that diagnosis code B1470 set because
connector D-25 or E-16 was engaged improperly.
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STEP 6. Check the seat belt pre-tensioner.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect seat belt pre-tensioner (LH) connector
E-16.
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(3)Connect special tool dummy resistor
(MB991865) to special tool resistor harness (MB991866). (4)Connect
special tool MB991866 to the E-16 harness side connector. (5)Connect the
negative battery terminal. (6)Erase the diagnosis code from memory, and
then check the diagnosis code.
Q.
Is diagnosis code B1470 set?
Go to Step 7.
Replace the seat
belt with pre-tensioner (LH) (Refer to ). Then go to Step
8.
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STEP 7. Check the seat belt pre-tensioner (LH) circuit. Resistance
measurement at the SRS-ECU connector D-25.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect SRS-ECU connector D-25.
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(3)
danger |
To prevent the seat belt pre-tensioner from
deploying unintentionally, disconnect the seat belt pre-tensioner (LH)
connector E-16 to short the squib circuit.
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Disconnect seat belt pre-tensioner (LH) connector E-16.
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(4)
caution |
Insert an insulator such as a cable tie to a depth
of 4mm 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 7, 8 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-25 harness side connector terminals
7 and 8. OK: Open circuit.
Q.
Is the check result normal?
Go to Step 8.
Repair the harness wires between
SRS-ECU connector D-25 (terminal No.7 and 8) and seat belt pre-tensioner
(LH) connector E-16 (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 B1470 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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