Lexus TechDoc

DTC B1653/35 Seat Position Airbag Sensor Circuit Malfunction

for Preparation Click here

DESCRIPTION

The seat position airbag sensor circuit consists of the airbag sensor assembly, front seat inner belt assembly LH (for LHD) or front seat inner belt assembly RH (for RHD) and seat position airbag sensor.
DTC B1653/35 is stored when a malfunction is detected in the seat position airbag sensor circuit.

DTC No.

DTC Detection Condition

Trouble Area

B1653/35

The airbag sensor assembly receives a line short circuit signal, an open circuit signal, a short circuit to ground signal or a short circuit to B+ signal in the seat position airbag sensor circuit.
Front seat inner belt assembly LH (for LHD) or front seat inner belt assembly RH (for RHD) malfunction
Seat position airbag sensor malfunction
Airbag sensor assembly malfunction

for LHD:

Floor wire
Front seat inner belt assembly LH
Seat position airbag sensor
Airbag sensor assembly

for RHD:

No. 2 floor wire
Front seat inner belt assembly RH
Seat position airbag sensor
Airbag sensor assembly

WIRING DIAGRAM

INSPECTION PROCEDURE

NOTICE:

After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work (Click here).

1.CHECK VEHICLE CONDITION

Check vehicle condition.
Result:
Result
Proceed to
LHD
A
RHD
B

Go to step 14

A

2.CHECK CONNECTORS

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Check that the connectors are properly connected to the airbag sensor assembly, front seat inner belt assembly LH and seat position airbag sensor.
OK:
The connectors are properly connected.
HINT:
If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

Disconnect the connectors from the airbag sensor assembly, front seat inner belt assembly LH and seat position airbag sensor.

Check that the terminals of the connectors are not damaged.
OK:
The terminals are not deformed or damaged.

REPLACE WIRE HARNESS

OK

3.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (OPEN)

Connect the connectors to the front seat inner belt assembly LH and floor wire.

Using SST, connect terminals 14 (LSP+) and 13 (LSP-) of connector B.
NOTICE:
Do not forcibly insert SST into the terminals of the connector when connecting the wire.

SST: 09843-18040

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
2 (LSP+) - 1 (LSP-)	Always	Below 1 Ω

Text in Illustration
*1	Seat Position Airbag Sensor	*2	Airbag Sensor Assembly
*3	Connector B	*4	Connector E
*a	Front view of wire harness connector (to Airbag Sensor Assembly)	*b	Front view of wire harness connector (to Seat Position Airbag Sensor)

Go to step 10

OK

4.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (SHORT)

Disconnect SST from connector B.

Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection
Condition
Specified Condition
2 (LSP+) - 1 (LSP-)
Always
1 MΩ or higher
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
*3
Connector E
*a
Front view of wire harness connector
(to Seat Position Airbag Sensor)

Go to step 11

OK

5.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (SHORT TO B+)

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG).

Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection
Switch Condition
Specified Condition
2 (LSP+) - Body ground
Power switch on (IG)
Below 1 V
1 (LSP-) - Body ground
Power switch on (IG)
Below 1 V
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
*3
Connector E
*a
Front view of wire harness connector
(to Seat Position Airbag Sensor)

Go to step 12

OK

6.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (SHORT TO GROUND)

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection
Condition
Specified Condition
2 (LSP+) - Body ground
Always
1 MΩ or higher
1 (LSP-) - Body ground
Always
1 MΩ or higher
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
*3
Connector E
*a
Front view of wire harness connector
(to Seat Position Airbag Sensor)

Go to step 13

OK

7.CHECK SEAT POSITION AIRBAG SENSOR

Connect the connectors to the airbag sensor assembly and seat position airbag sensor.

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG), and wait for at least 60 seconds.

Clear the DTCs stored in memory (Click here).

Turn the power switch off.

Turn the power switch on (IG), and wait for at least 60 seconds.

Check for DTCs (Click here).
OK:
DTC B1653/35 is not output.
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
HINT:
Codes other than DTC B1653/35 may be output at this time, but they are not related to this check.

Go to step 8

USE SIMULATION METHOD TO CHECK (Click here)

8.REPLACE SEAT POSITION AIRBAG SENSOR

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Replace the seat position airbag sensor with a known good one (Click here).
HINT:
Perform the following inspection using known good parts from another vehicle if possible.

NEXT

9.CHECK AIRBAG SENSOR ASSEMBLY

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG), and wait for at least 60 seconds.

Clear the DTCs stored in memory (Click here).

Turn the power switch off.

Turn the power switch on (IG), and wait for at least 60 seconds.

Check for DTCs (Click here).
OK:
DTC B1653/35 is not output.
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
HINT:
Codes other than DTC B1653/35 may be output at this time, but they are not related to this check.

REPLACE AIRBAG SENSOR ASSEMBLY (Click here)

END

10.CHECK FLOOR WIRE (OPEN)

Disconnect the floor wire from the front seat inner belt assembly LH.

HINT:
SST has already been inserted into connector B.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
P3-4 (LSP+) - P3-3 (LSP-)	Always	Below 1 Ω

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor	*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly LH	*4	Floor Wire
*5	Connector B	*6	Connector C
*a	Front view of wire harness connector (to Airbag Sensor Assembly)	*b	Front view of wire harness connector (to Front Seat Inner Belt Assembly LH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH (Click here)

REPLACE FLOOR WIRE

11.CHECK FLOOR WIRE (SHORT)

Disconnect the floor wire from the front seat inner belt assembly LH.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
P3-4 (LSP+) - P3-3 (LSP-)	Always	1 MΩ or higher

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor
*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly LH
*4	Floor Wire
*5	Connector C
*a	Front view of wire harness connector (to Front Seat Inner Belt Assembly LH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH (Click here)

REPLACE FLOOR WIRE

12.CHECK FLOOR WIRE (SHORT TO B+)

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Disconnect the floor wire from the front seat inner belt assembly LH.

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
P3-4 (LSP+) - Body ground	Power switch on (IG)	Below 1 V
P3-3 (LSP-) - Body ground	Power switch on (IG)	Below 1 V

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor
*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly LH
*4	Floor Wire
*5	Connector C
*a	Front view of wire harness connector (to Front Seat Inner Belt Assembly LH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH (Click here)

REPLACE FLOOR WIRE

13.CHECK FLOOR WIRE (SHORT TO GROUND)

Disconnect the floor wire from the front seat inner belt assembly LH.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
P3-4 (LSP+) - Body ground	Always	1 MΩ or higher
P3-3 (LSP-) - Body ground	Always	1 MΩ or higher

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor
*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly LH
*4	Floor Wire
*5	Connector C
*a	Front view of wire harness connector (to Front Seat Inner Belt Assembly LH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH (Click here)

REPLACE FLOOR WIRE

14.CHECK CONNECTORS

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Check that the connectors are properly connected to the airbag sensor assembly, front seat inner belt assembly RH and seat position airbag sensor.
OK:
The connectors are properly connected.
HINT:
If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

Disconnect the connectors from the airbag sensor assembly, front seat inner belt assembly RH and seat position airbag sensor.

Check that the terminals of the connectors are not damaged.
OK:
The terminals are not deformed or damaged.

REPLACE WIRE HARNESS

OK

15.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (OPEN)

Connect the connectors to the front seat inner belt assembly RH and No. 2 floor wire.

Using SST, connect terminals 12 (RSP+) and 13 (RSP-) of connector B.
NOTICE:
Do not forcibly insert SST into the terminals of the connector when connecting the wire.

SST: 09843-18040

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
2 (RSP+) - 1 (RSP-)	Always	Below 1 Ω

Text in Illustration
*1	Seat Position Airbag Sensor	*2	Airbag Sensor Assembly
*3	Connector B	*4	Connector E
*a	Front view of wire harness connector (to Airbag Sensor Assembly)	*b	Front view of wire harness connector (to Seat Position Airbag Sensor)

Go to step 22

OK

16.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (SHORT)

Disconnect SST from connector B.

Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection
Condition
Specified Condition
2 (RSP+) - 1 (RSP-)
Always
1 MΩ or higher
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
*3
Connector E
*a
Front view of wire harness connector
(to Seat Position Airbag Sensor)

Go to step 23

OK

17.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (SHORT TO B+)

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG).

Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection
Switch Condition
Specified Condition
2 (RSP+) - Body ground
Power switch on (IG)
Below 1 V
1 (RSP-) - Body ground
Power switch on (IG)
Below 1 V
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
*3
Connector E
*a
Front view of wire harness connector
(to Seat Position Airbag Sensor)

Go to step 24

OK

18.CHECK SEAT POSITION AIRBAG SENSOR CIRCUIT (SHORT TO GROUND)

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection
Condition
Specified Condition
2 (RSP+) - Body ground
Always
1 MΩ or higher
1 (RSP-) - Body ground
Always
1 MΩ or higher
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
*3
Connector E
*a
Front view of wire harness connector
(to Seat Position Airbag Sensor)

Go to step 25

OK

19.CHECK SEAT POSITION AIRBAG SENSOR

Connect the connectors to the airbag sensor assembly and seat position airbag sensor.

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG), and wait for at least 60 seconds.

Clear the DTCs stored in memory (Click here).

Turn the power switch off.

Turn the power switch on (IG), and wait for at least 60 seconds.

Check for DTCs (Click here).
OK:
DTC B1653/35 is not output.
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
HINT:
Codes other than DTC B1653/35 may be output at this time, but they are not related to this check.

Go to step 20

USE SIMULATION METHOD TO CHECK (Click here)

20.REPLACE SEAT POSITION AIRBAG SENSOR

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Replace the seat position airbag sensor with a known good one (Click here).
HINT:
Perform the following inspection using known good parts from another vehicle if possible.

NEXT

21.CHECK AIRBAG SENSOR ASSEMBLY

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG), and wait for at least 60 seconds.

Clear the DTCs stored in memory (Click here).

Turn the power switch off.

Turn the power switch on (IG), and wait for at least 60 seconds.

Check for DTCs (Click here).
OK:
DTC B1653/35 is not output.
Text in Illustration
*1
Seat Position Airbag Sensor
*2
Airbag Sensor Assembly
HINT:
Codes other than DTC B1653/35 may be output at this time, but they are not related to this check.

REPLACE AIRBAG SENSOR ASSEMBLY (Click here)

END

22.CHECK NO. 2 FLOOR WIRE (OPEN)

Disconnect the No. 2 floor wire from the front seat inner belt assembly RH.

HINT:
SST has already been inserted into connector B.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
Q19-4 (RSP+) - Q19-3 (RSP-)	Always	Below 1 Ω

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor	*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly RH	*4	No. 2 Floor Wire
*5	Connector B	*6	Connector C
*a	Front view of wire harness connector (to Airbag Sensor Assembly)	*b	Front view of wire harness connector (to Front Seat Inner Belt Assembly RH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH (Click here)

REPLACE NO. 2 FLOOR WIRE

23.CHECK NO. 2 FLOOR WIRE (SHORT)

Disconnect the No. 2 floor wire from the front seat inner belt assembly RH.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
Q19-4 (RSP+) - Q19-3 (RSP-)	Always	1 MΩ or higher

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor
*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly RH
*4	No. 2 Floor Wire
*5	Connector C
*a	Front view of wire harness connector (to Front Seat Inner Belt Assembly RH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH (Click here)

REPLACE NO. 2 FLOOR WIRE

24.CHECK NO. 2 FLOOR WIRE (SHORT TO B+)

Turn the power switch off.

Disconnect the cable from the negative (-) auxiliary battery terminal.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

Disconnect the No. 2 floor wire from the front seat inner belt assembly RH.

Connect the cable to the negative (-) auxiliary battery terminal.

Turn the power switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
Q19-4 (RSP+) - Body ground	Power switch on (IG)	Below 1 V
Q19-3 (RSP-) - Body ground	Power switch on (IG)	Below 1 V

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor
*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly RH
*4	No. 2 Floor Wire
*5	Connector C
*a	Front view of wire harness connector (to Front Seat Inner Belt Assembly RH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH (Click here)

REPLACE NO. 2 FLOOR WIRE

25.CHECK NO. 2 FLOOR WIRE (SHORT TO GROUND)

Disconnect the No. 2 floor wire from the front seat inner belt assembly RH.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
Q19-4 (RSP+) - Body ground	Always	1 MΩ or higher
Q19-3 (RSP-) - Body ground	Always	1 MΩ or higher

Result
Result	Proceed to
NG	A
OK (for Manual seat)	B
OK (for Power seat)	C

Text in Illustration
*1	Seat Position Airbag Sensor
*2	Airbag Sensor Assembly
*3	Front Seat Inner Belt Assembly RH
*4	No. 2 Floor Wire
*5	Connector C
*a	Front view of wire harness connector (to Front Seat Inner Belt Assembly RH)

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH (Click here)

REPLACE NO. 2 FLOOR WIRE

Result	Proceed to
LHD	A
RHD	B