Code No. B1603: Seat
belt pre-tensioner (driver’s side) (squib) system (short
circuit between squib circuit
terminals)
| caution |
If the diagnosis code No.
B1603 is set to SRS-ECU, be sure to diagnose the CAN bus
line.
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Only when the frontal impact
exceeding the threshold is simultaneously detected (turned
ON) by the front impact sensor as well as by the analogue
G-sensor and safing G-sensor in SRS-ECU,
the electric current is supplied from SRS-ECU to the seat
belt pre-tensioner (squib).
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The code is set when the short
circuit occurs between the terminals of SRS-ECU seat belt
pre-tensioner (driver’s side) (squib)
circuit.
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- Damaged short spring *
- Short circuit between terminals of seat belt
pre-tensioner (driver’s side)
(squib) circuit
- Damaged connector(s)
- Malfunction of SRS-ECU
- Insufficient press of locking button or locking
button not pressed
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| note |
*: The squib circuit
connectors integrate a short spring (which
prevents the
seat belt pre-tensioner from being
unintentionally deployed because of static
electricity by shorting
the positive wire to the earth wire in the squib
circuit when the connectors are disconnected).
Therefore, when the above codes are set, the
short spring may not be released due to the
damaged
connector even when the connectors are
connected.
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STEP 1. M.U.T.-III CAN bus diagnostics.
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Use 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 54C - Troubleshooting  ).
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STEP 2. Check whether the diagnosis code is
reset.
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(1)Connect the negative battery terminal.
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(2)After erasing the diagnosis code memory, check
the diagnosis code again.
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(3)Disconnect the negative battery
terminal.
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Q.
Is the diagnosis code No. B1603 set?
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Go to Step
3.
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Intermittent
malfunction.
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STEP 3. Connector check: SRS-ECU connector, seat belt
pre-tensioner
(driver’s side) connector.
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(1)Check that the negative battery terminal is
disconnected. If the negative battery
terminal is connected, disconnect it.
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(2)Disconnecting the SRS-ECU connector, connect it
again.
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(3) After disconnecting the SRS-ECU
harness side connector, connect the connector again.
For the seat belt pre-tensioner (driver’s side)
harness side connector disconnection,
use the flat-tipped screwdriver to pull out the harness side
connector locking button. After
releasing the lock, disconnect the harness side
connector.
(4)Connect the negative battery
terminal.
(5)After erasing the diagnosis code memory,
check the diagnosis code again.
(6)Disconnect the
negative battery terminal.
Q.
Is the diagnosis code No. B1603 set?
Go to Step
4.
Replace
the connector concerned.
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STEP 4. Diagnosis check by dummy resistor
connection.
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(1)Check that the negative battery terminal is
disconnected. If the negative battery
terminal is connected, disconnect it.
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(2)Use the flat-tipped screwdriver
to pull out the locking button of harness side connector.
After releasing the lock, disconnect the seat belt
pre-tensioner (driver’s side) harness
side connector.
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(3)Connect special tool dummy
resistor (MB991865) to special tool resistor harness
(MB991884).
(4)Connect special tool resistor harness to
the seat belt pre-tensioner (driver’s
side) harness side connector.
(5)Connect the negative
battery terminal.
(6)After erasing the diagnosis code
memory, check the diagnosis code again.
(7)Disconnect the
negative battery terminal.
Q.
Is the diagnosis code No. B1603 set?
Go to Step
5.
Replace
the seat belt with pre-tensioner (driver’s
side).
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STEP 5. Resistance check at the SRS-ECU connector
(PTD+,
PTD- line).
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(1)Check that the negative battery terminal is
disconnected. If the negative battery
terminal is connected, disconnect it.
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(2)Disconnect the SRS-ECU connector.
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(3)
| danger |
To release the SRS-ECU
connector short spring in the following
operations, disconnect this seat belt
pre-tensioner connector, and keep the squib
circuit shorted.
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Use the flat-tipped screwdriver to pull out the
locking button of harness side connector.
After releasing the lock, disconnect the seat belt
pre-tensioner (driver’s side) harness
side connector.
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(4)
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The short spring may not be
released due to the insufficient insertion.
Therefore, insert
the insulator for 4 mm or more.
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Insert an insulator (width: 3 mm, thickness: 0.5 mm)
such as cable tie PTD+,
PTD- line between the SRS-ECU connector and the seat belt
pre-tensioner (RH) connector.
(5)Take the measurements
below at the SRS-ECU harness side connector.
- Continuity PTD+, PTD- line between the SRS-ECU
connector
and the seat belt pre-tensioner (RH)
connector.
OK: No continuity
Q.
Is the check result normal?
Go to Step
6.
Repair
the wiring harness PTD+, PTD- line between the SRS-ECU
connector
and the seat belt pre-tensioner (RH) connector.
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STEP 6. Check whether the diagnosis code is
reset.
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Q.
Is the diagnosis code No. B1603 set?
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Replace
SRS-ECU.
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Intermittent
malfunction.
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