SUPPLEMENTAL RESTRAINT SYSTEMS: AIRBAG SYSTEM (for Gasoline Model): B1637,B1638; Curtain Shield Airbag Sensor Lost Communication (LH); 2019 - 2022 MY Avalon [04/2018

Last Modified: 08-21-2023	6.11:8.1.0	Doc ID: RM100000001BKC3
Model Year Start: 2019	Model: Avalon	Prod Date Range: [04/2018 - ]
Title: SUPPLEMENTAL RESTRAINT SYSTEMS: AIRBAG SYSTEM (for Gasoline Model): B1637,B1638; Curtain Shield Airbag Sensor Lost Communication (LH); 2019 - 2022 MY Avalon [04/2018 - ]

DTC

B1637

Curtain Shield Airbag Sensor Lost Communication (LH)

DTC

B1638

Curtain Shield Airbag Sensor Initialization Error (LH)

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.

CONNECT CONNECTORS PROPERLY

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.

REPLACE FLOOR WIRE OR FRONT DOOR WIRE LH

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).

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

REPLACE FLOOR WIRE

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.

(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

GO TO STEP 7

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.

(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.

REPLACE SIDE NO. 2 AIRBAG SENSOR LH

USE SIMULATION METHOD TO CHECK

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.

(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.

REPLACE AIRBAG ECU ASSEMBLY

REPLACE SIDE AIRBAG PRESSURE SENSOR LH

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.

(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

REPLACE FRONT DOOR WIRE LH

REPLACE FLOOR WIRE