Code No. B1570: Passenger’s air bag cut off switch malfunction
Code No. B1574: Passenger’s air bag cut off switch circuit open
Code No. B1575: Passenger’s air bag cut off switch circuit (earth side) shorted
Code No. B1576: Passenger’s air bag cut off switch circuit (power supply side) shorted
code No. B1581: Incorrect passenger’s air bag cut off switch
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If diagnosis code B1570, B1574, B1575, B1576 or B1581 is set in the SRS-ECU, always diagnose the CAN bus lines.
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OPERATION
According to the passenger’s air bag cut off switch connecting position, the SRS-ECU judges the deployment and non-deployment of passenger’s (front) air bag.
DIAGNOSIS CODE SET CONDITIONS
Diagnosis code is set when the resistance between input terminals of the passenger’s air bag cut off switch is without the standard value.
Cause of trouble in each diagnosis code is as follows.
Code No.
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Symptom
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B1570
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Malfunction of passenger’s air bag cut off switch
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B1574
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Malfunction of the common terminal or open circuit in its harness
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B1575
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Short to body earth in the common terminal harness
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B1576
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Short to the power supply in the common terminal harness
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B1581
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Mismatch between vehicle and passenger’s air bag cut off switch specifications.
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PROBABLE CAUSES
- Malfunction of the passenger’s air bag cut off switch
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C, Diagnosis-CAN Bus Diagnostic Chart 
).
STEP 2. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set.
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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.B1570, B1574, B1575, B1576 or B1581 set?
Go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
STEP 3. Check the passenger’s air bag cut off switch.
Check of a passenger’s air bag cut off switch (Refer to ).
Q.
Is the check result normal?
Go to Step 4.
Replace passenger’s air bag cut off switch (Refer to ).
STEP 4. Check the passenger’s air bag cut off switch circuit. Resistance measurement at 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)Switch the passenger’s air bag cut off switch to air bag ON side.
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(4)Measure the resistance between POF-, POFO line.
OK: 820 ± 20 Ω
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(5)Switch the passenger’s air bag cut off switch to air bag OFF side.
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(6)Measure the resistance between POF-, POFO line.
OK: Continuity (less than 2 Ω)
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Q.
Is the check result normal?
Go to Step 5.
Repair the harness wires POF-, POFO line between SRS-ECU connector and passenger’s air bag cut off switch connector.
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)Disconnect the passenger’s air bag cut off switch connector.
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(4)Take the measurements below at the SRS-ECU harness side connector.
- Continuity between POF-, POFO line and body earth
OK: No continuity
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Q.
Is the check result normal?
Go to Step 6.
Repair the harness wires POF-, POFO line between SRS-ECU connector and passenger’s air bag cut off switch connector.
STEP 6. Voltage 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)Disconnect the passenger’s air bag cut off switch connector.
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(4)Connect the negative battery terminal.
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(6)Take the measurements below at the SRS-ECU harness side connector.
- Voltage between POF-, POFO line and body earth
OK: 1 V or less
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Q.
Is the check result normal?
Go to Step 7.
Repair the harness wires POF-, POFO line between SRS-ECU connector and passenger’s air bag cut off switch connector.
STEP 7. Check whether the diagnosis code is set again.
Q.
Is diagnosis code No.B1570, B1574, B1575, B1576 or B1581 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).