Code No.B1603 Seat belt pre-tensioner (driver’s side) (squib)
system (short circuit between squib circuit terminals)
| caution |
If diagnosis code B1603 is set in the
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 set
again.
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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 diagnosis code No. B1603 set?
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Go to Step
3.
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Intermittent
malfunction (Refer to GROUP 00 - How to Use
Troubleshooting/Inspection Service Points - How
to Cope with 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)After disconnecting the SRS-ECU connector,
connect it again.
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(3) After disconnecting the seat
belt pre-tensioner (driver’s side) 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 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 diagnosis code No. B1603 set?
Go to Step
5.
Replace
the seat belt with pre-tensioner (driver’s side)
(Refer to ).
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STEP 5. Resistance measurement at the SRS-ECU
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)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)
| caution |
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 between the PTD+, PTD- line and the
short spring, and release the short spring.
(5)Take the
measurements below at the SRS-ECU harness side connector.
- Continuity between PTD+, PTD- line
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 (driver’s
side) connector.
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STEP 6. Check whether the diagnosis code is set
again.
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Q.
Is diagnosis code No. B1603 set?
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Replace SRS-ECU
(Refer to ).
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Intermittent
malfunction (Refer to GROUP 00 - How to Use
Troubleshooting/Inspection Service Points - How
to Cope with Intermittent Malfunction ).
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