Code No.B1633 Knee air bag module (squib) system (shorted to squib circuit
earth)
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- If diagnosis code B1633 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 knee air bag module
(squib).
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The code is set when the SRS-ECU knee air bag
module (squib) circuit is shorted to earth.
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- Damaged wiring harness and connectors
- Knee air bag module (squib) harness shorted to earth
- 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 codes No. B1633 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 wiring harness side connector, and release the
lock.
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(3)Connect the dummy resistor (Special tool:
MB991865) to the resistor harness (Special tool: MB991884).
(4)Connect
the resistor harness (special tool) to right curtain air bag module
connector.
(5)Connect the negative battery terminal.
(6)After erasing
the diagnosis code memory, check the diagnosis code again.
Q.
Is diagnosis code No. B1633 set?
Go to Step 4.
Replace the knee air bag module (Refer
to ).
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STEP 4. 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 connector short spring in the
following operations, disconnect this harness side connector, and keep
the squib circuit shorted.
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Use the flat-tipped screwdriver to pull out the locking button of
wiring harness side connector, and release the lock.
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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 KDS+, KDS- line, and then release the short
spring.
(5)Take the measurements below at the harness side
connector.
- Continuity between KDS+, KDS- line and body earth
OK: No continuity
Q.
Is the check result normal?
Go to Step 5.
Repair KDS+, KDS- line between
the SRS-ECU connector and the knee air bag module connector.
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STEP 5. Check whether the diagnosis code is set again.
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Q.
Is diagnosis code No. B1633 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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