Code No. B1502 Right rear curtain air bag module (squib) system (shorted
to squib circuit earth) <Vehicles with rear curtain air
bag>
| caution |
If diagnosis code No. B1502 is set in the SRS-ECU, be
sure to diagnose the CAN bus line.
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OPERATION
In case of side collision, when the impact exceeding the
threshold is applied to the vehicle, and when the impact is simultaneously
detected (turned ON) by the side impact sensor as well as by the analogue
G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the rear
curtain air bag module (squib) of impacted side.
TROUBLE JUDGEMENT
The code is set when the SRS-ECU rear curtain
air bag module (squib) circuit is shorted to earth.
PROBABLE CAUSES
- Damaged wiring harness and connector
- rear curtain 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 code No. B1502 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 connected, disconnect the negative battery terminal.
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(2)Disconnect the right rear curtain airbag module
connector.
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(3)Connect special tool dummy resistor
(MB991865) to special tool resistor harness (MB991866).
(4)
| caution |
Do not insert a probe directly into the terminal
from the connector front side as the connector contact pressure may be
weakened.
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Insert the resistor harness probe from the back of right rear
curtain airbag module 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. B1502 set?
Go to Step 4.
Replace the right rear curtain air bag
module.
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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)While pushing the part "A" indicated in the
figure of the harness side connector, turn the lock lever to the direction
of the arrow to release the lock lever. After disconnect the SRS-ECU
connector.
(3)
| danger |
To release SRS-ECU wiring harness side connector
short spring in the following operations, disconnect rear curtain air
bag module connector in advance, and keep the squib circuit
shorted.
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Disconnect the right rear curtain airbag module 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 CR2-, CR2+ line and the short spring, and release the
short spring.
(5)Check the continuity between the SRS-ECU wiring harness
side connector CR2-, CR2+ line.
OK: No
continuity
Q.
Is the check result normal?
Go to Step 5.
Repair the wiring
harness.
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STEP 5. Check whether the diagnosis code is set again.
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Q.
Is diagnosis code No. B1502 set?
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Replace SRS-ECU.
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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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