Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Curtain Shield Airbag Sensor Lost Communication (LH) (B1637,B1638)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System(for Gasoline Model) / Curtain Shield Airbag Sensor Lost Communication (LH) (B1637,B1638)

DESCRIPTION

The side collision sensor LH circuit (bus 1) consists of the airbag ECU assembly, side airbag pressure sensor LH and side No. 2 airbag sensor LH.

The side airbag pressure sensor LH and side No. 2 airbag sensor LH detect impacts to the vehicle and send signals to the airbag ECU assembly to determine if the airbags and pretensioners should be deployed.

These DTCs are stored when a malfunction is detected in the side collision sensor LH circuit (bus 1).

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Warning Indicate

Test Mode / Check Mode

B1637

Curtain Shield Airbag Sensor Lost Communication (LH)
  • The airbag ECU assembly detects a line short, short to ground or B+, or an open in the side collision sensor LH circuit (bus 1).
  • Side airbag pressure sensor LH malfunction
  • Side No. 2 airbag sensor LH malfunction
  • Airbag ECU assembly malfunction
  • Floor wire
  • Front door wire LH
  • Side airbag pressure sensor LH
  • Side No. 2 airbag sensor LH
  • Airbag ECU assembly

Comes on

Does not apply to test/check mode

B1638

Curtain Shield Airbag Sensor Initialization Error (LH)
  • The airbag ECU assembly detects a line short, short to ground or B+, or an open in the side collision sensor LH circuit (bus 1).
  • Side airbag pressure sensor LH malfunction
  • Side No. 2 airbag sensor LH malfunction
  • Airbag ECU assembly malfunction
  • Floor wire
  • Front door wire LH
  • Side airbag pressure sensor LH
  • Side No. 2 airbag sensor LH
  • Airbag ECU assembly

Comes on

Does not apply to test/check mode

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

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

Click here

PROCEDURE

1.

CHECK CONNECTION OF CONNECTORS

(a) Turn the engine switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

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

(c) Check that the connectors are properly connected to the airbag ECU assembly, side airbag pressure sensor LH and side No. 2 airbag sensor LH. Also check that the connectors that link the floor wire and front door wire LH are properly connected.

OK:

The connectors are properly connected.

NG

CONNECT CONNECTORS PROPERLY
OK

2.

CHECK CONNECTORS

(a) Disconnect the connectors from the airbag ECU assembly, side airbag pressure sensor LH and side No. 2 airbag sensor LH. Also disconnect the connectors that link the floor wire and front door wire LH.

(b) Check that the terminals of the connectors are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPLACE FLOOR WIRE OR FRONT DOOR WIRE LH
OK

3.

CHECK FLOOR WIRE

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

*1

Side No. 2 Airbag Sensor LH

*2

Airbag ECU Assembly

*3

Floor Wire

*4

Service Wire

*a

Front view of wire harness connector

(to Airbag ECU Assembly)

*b

Front view of wire harness connector

(to Side No. 2 Airbag Sensor LH)

(b) Turn the engine switch on (IG).

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

K31-4 (BCL+) - Body ground

Engine switch on (IG)

Below 1 V

K31-3 (BCL-) - Body ground

Engine switch on (IG)

Below 1 V

(d) Turn the engine switch off.

(e) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

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

(f) Using a service wire, connect terminals 32 (BBL+) and 31 (BBL-) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

K31-4 (BCL+) - K31-3 (BCL-)

Always

Below 1 Ω

(h) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

K31-4 (BCL+) - K31-3 (BCL-)

Always

1 MΩ or higher

K31-4 (BCL+) - Body ground

Always

1 MΩ or higher

K31-3 (BCL-) - Body ground

Always

1 MΩ or higher
NG

REPLACE FLOOR WIRE
OK

4.

CHECK WIRE HARNESS

(a) Connect the connectors that link the floor wire and front door wire LH.

*1

Side Airbag Pressure Sensor LH

*2

Side No. 2 Airbag Sensor LH

*3

Front Door Wire LH

*4

Floor Wire

*5

Service Wire

*a

Front view of wire harness connector

(to Side No. 2 Airbag Sensor LH)

*b

Front view of wire harness connector

(to Side Airbag Pressure Sensor LH)

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

(c) Turn the engine switch on (IG).

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

K31-1 (BDL+) - Body ground

Engine switch on (IG)

Below 1 V

K31-2 (BDL-) - Body ground

Engine switch on (IG)

Below 1 V

(e) Turn the engine switch off.

(f) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

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

(g) Using a service wire, connect terminals 2 (BDL+) and 1 (BDL-) of connector E.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

K31-1 (BDL+) - K31-2 (BDL-)

Always

Below 1 Ω

(i) Disconnect the service wire from connector E.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

K31-1 (BDL+) - K31-2 (BDL-)

Always

1 MΩ or higher

K31-1 (BDL+) - Body ground

Always

1 MΩ or higher

K31-2 (BDL-) - Body ground

Always

1 MΩ or higher
NG

GO TO STEP 7

OK

5.

CHECK SIDE NO. 2 AIRBAG SENSOR LH

(a) Connect the connectors to the side airbag pressure sensor LH and airbag ECU assembly.

*1

Side No. 2 Airbag Sensor RH

*2

Airbag ECU Assembly

(b) Interchange the side No. 2 airbag sensor LH with RH and connect the connectors.

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

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

(e) Clear the DTCs stored in memory.

Body Electrical > SRS Airbag > Clear DTCs

(f) Turn the engine switch off.

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

(h) Check for DTCs.

Body Electrical > SRS Airbag > Trouble Codes

HINT:

Codes other than DTCs B1632, B1633, B1637 and B1638 may be output at this time, but they are not related to this check.

Result

Proceed to

DTC B1637 or B1638 is output.

A

DTC B1632 or B1633 is output.

B

DTCs B1632, B1633, B1637 and B1638 are not output.

C

(i) Turn the engine switch off.

(j) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

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

(k) Return the side No. 2 airbag sensor LH and RH to their original positions and connect the connectors.

B

REPLACE SIDE NO. 2 AIRBAG SENSOR LH

C

USE SIMULATION METHOD TO CHECK

A

6.

CHECK SIDE AIRBAG PRESSURE SENSOR LH

(a) Interchange the side airbag pressure sensor LH with RH and connect the connectors.

*1

Side Airbag Pressure Sensor RH

*2

Side No. 2 Airbag Sensor LH

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

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

(d) Clear the DTCs stored in memory.

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the engine switch off.

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

(g) Check for DTCs.

Body Electrical > SRS Airbag > Trouble Codes

HINT:

Codes other than DTCs B1632, B1633, B1637 and B1638 may be output at this time, but they are not related to this check.

Result

Proceed to

DTC B1637 or B1638 is output.

A

DTC B1632 or B1633 is output.

B

DTCs B1632, B1633, B1637 and B1638 are not output.

C

(h) Turn the engine switch off.

(i) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

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

(j) Return the side airbag pressure sensor LH and RH to their original positions and connect the connectors.

A

REPLACE AIRBAG ECU ASSEMBLY

B

REPLACE SIDE AIRBAG PRESSURE SENSOR LH

C

USE SIMULATION METHOD TO CHECK

7.

CHECK FLOOR WIRE

(a) Disconnect the floor wire connector from the front door wire LH.

*1

Side Airbag Pressure Sensor LH

*2

Side No. 2 Airbag Sensor LH

*3

Front Door Wire LH

*4

Floor Wire

*5

Service Wire

*a

Front view of wire harness connector

(to Side No. 2 Airbag Sensor LH)

*b

Front view of wire harness connector

(to Front Door Wire LH)

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

(c) Turn the engine switch on (IG).

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

IK2-23 (BDL+) - Body ground

Engine switch on (IG)

Below 1 V

IK2-41 (BDL-) - Body ground

Engine switch on (IG)

Below 1 V

(e) Turn the engine switch off.

(f) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

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

(g) Using a service wire, connect terminals 1 (BDL+) and 2 (BDL-) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

IK2-23 (BDL+) - IK2-41 (BDL-)

Always

Below 1 Ω

(i) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

IK2-23 (BDL+) - IK2-41 (BDL-)

Always

1 MΩ or higher

IK2-23 (BDL+) - Body ground

Always

1 MΩ or higher

IK2-41 (BDL-) - Body ground

Always

1 MΩ or higher
OK

REPLACE FRONT DOOR WIRE LH
NG

REPLACE FLOOR WIRE
    Curtain Shield Airbag Sensor (LH) (B1635)

    Occupant Classification System Malfunction (B1650,B165A)

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