Code No. B1620 Driver’s lap pre-tensioner (squib) system (open
circuit of squib circuit)
| caution |
If diagnosis code No. B1620 is set in the SRS-ECU, be
sure to diagnose the CAN bus line.
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OPERATION
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 in SRS-ECU, the electric current is supplied from
SRS-ECU to the lap pre-tensioner (squib).
TROUBLE JUDGEMENT
The code is set when the open circuit occurs to
the SRS-ECU driver’s lap pre-tensioner (squib) circuit.
PROBABLE CAUSES
- Poor contact of connector
- Open circuit to lap pre-tensioner (squib) circuit
- Malfunction of SRS-ECU
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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. B1620 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. 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 lap pre-tensioner harness side connector.
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(3)Connect the special tool dummy resistor
(MB991865) to the special tool resistor harness (MB991884).
(4)Connect
the special tool resistor harness to the lap pre-tensioner 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. B1620 set?
Go to Step 4.
Replace the seat belt with
pre-tensioner (Refer to ).
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STEP 4. Resistance measurement at the SRS-ECU connector and the lap
pre-tensioner 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 lap 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 lap
pre-tensioner 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 between the PD2+, PD2-, and then release the short
spring.
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(5)Connect special tool resistor harness
(MB991884) to the removed lap pre-tensioner harness side
connector.
(6)Take the measurements below at the resistor harness and
SRS-ECU harness side connector.
- Continuity PD2+ line between SRS-ECU connector and lap
pre-tensioner harness connector
- Continuity PD2- line between SRS-ECU connector and lap pre-tensioner
harness connector
OK: Continuity (less than 2 Ω)
Q.
Is the check result normal?
Go to Step 5.
Repair the wiring harness PD2+,
PD2- line between the SRS-ECU connector and the lap pre-tensioner
connector.
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STEP 5. Check whether the diagnosis code is set again.
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Q.
Is diagnosis code No. B1620 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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