SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM (for TMMMS Made): B1780; Front Occupant Classification Sensor LH Circuit Malfunction; 2023 MY Corolla Corolla Hatchback Corolla HV GR Corolla [09/2022

Last Modified: 05-13-2024	6.11:8.1.0	Doc ID: RM10000000259TS
Model Year Start: 2023	Model: GR Corolla	Prod Date Range: [09/2022 - 11/2022]
Title: SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM (for TMMMS Made): B1780; Front Occupant Classification Sensor LH Circuit Malfunction; 2023 MY Corolla Corolla Hatchback Corolla HV GR Corolla [09/2022 - 11/2022]

DTC

B1780

Front Occupant Classification Sensor LH Circuit Malfunction

DESCRIPTION

The front occupant classification sensor LH circuit consists of the occupant detection ECU and front occupant classification sensor LH.

DTC B1780 is stored when a malfunction is detected in the front occupant classification sensor LH circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B1780	Front Occupant Classification Sensor LH Circuit Malfunction	The occupant detection ECU detects a line short, short to ground or B+, or an open in the front occupant classification sensor LH circuit. Front occupant classification sensor LH malfunction Occupant detection ECU malfunction	Front seat wire RH Front occupant classification sensor LH (Separate type front seat cushion spring assembly RH) Occupant detection ECU

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After the ignition switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.
Click here

HINT:

When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

Click here

HINT:

When DTC B1650 is stored as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant detection ECU. When DTC B1780 is output, perform troubleshooting for this DTC first.
If it is difficult to perform troubleshooting (wire harness inspection), remove the front passenger seat installation bolts to see under the seat cushion.
In the above case, lift and hold the seat so that it does not fall down. Hold the seat only as necessary because holding the seat for a long period of time may cause seat rail deformation.

PROCEDURE

1.	CHECK CONNECTORS

(a) Turn the ignition switch off.

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

(c) Check that the connectors are properly connected to the occupant detection ECU and front occupant classification sensor LH.

OK:

The connectors are properly connected.

HINT:

If the connectors are not properly connected, reconnect the connectors and proceed to the next inspection.

(d) Disconnect the connectors from the occupant detection ECU and front occupant classification sensor LH.

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

OK:

The terminals are not deformed or damaged.

REPLACE FRONT SEAT WIRE RH

2.	CHECK FRONT SEAT WIRE RH

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

*1	Front Occupant Classification Sensor LH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Service Wire
*a	Front view of wire harness connector (to Occupant Detection ECU)
*b	Front view of wire harness connector (to Front Occupant Classification Sensor LH)

(b) Turn the ignition switch to ON.

Standard Voltage:

Tester Connection	Condition	Specified Condition
j3-1 (SVC1) - Body ground	Ignition switch ON	Below 1 V
j3-3 (SIG1) - Body ground	Ignition switch ON	Below 1 V
j3-5 (SGD1) - Body ground	Ignition switch ON	Below 1 V

(d) Turn the ignition switch off.

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

(f) Using service wires, connect terminals 1 (SVC) and 3 (SGD), and terminals 2 (SIG) and 3 (SGD) of connector C.

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
j3-1 (SVC1) - j3-5 (SGD1)	Always	Below 1 Ω
j3-3 (SIG1) - j3-5 (SGD1)	Always	Below 1 Ω

(h) Disconnect the service wires from connector C.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
j3-1 (SVC1) - j3-5 (SGD1)	Always	1 MΩ or higher
j3-3 (SIG1) - j3-5 (SGD1)	Always	1 MΩ or higher
j3-1 (SVC1) - j3-3 (SIG1)	Always	1 MΩ or higher
j3-1 (SVC1) - Body ground	Always	1 MΩ or higher
j3-3 (SIG1) - Body ground	Always	1 MΩ or higher
j3-5 (SGD1) - Body ground	Always	1 MΩ or higher

REPLACE FRONT SEAT WIRE RH

CHECK DTC

(a) Connect the connectors to the occupant detection ECU and front occupant classification sensor LH.

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

(d) Clear the DTCs stored in the occupant detection ECU.

Body Electrical > Occupant Detection > Clear DTCs

(e) Clear the DTCs stored in the airbag sensor assembly.

Body Electrical > SRS Airbag > Clear DTCs

(f) Turn the ignition switch off.

(g) Turn the ignition switch to ON, and wait for at least 10 seconds.

(h) Check for DTCs.

Body Electrical > Occupant Detection > Trouble Codes

OK:

DTC B1780 is not output.

HINT:

Codes other than DTC B1780 may be output at this time, but they are not related to this check.

(i) Turn the ignition switch off.

USE SIMULATION METHOD TO CHECK

4.	CHECK OCCUPANT DETECTION ECU

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

(b) Replace the occupant detection ECU with a known good one.

Click here

HINT:

Perform the following inspection using known good parts from another vehicle if possible.

(d) Turn the ignition switch to ON, and wait for at least 60 seconds.

(e) Clear the DTCs stored in the occupant detection ECU.

Body Electrical > Occupant Detection > Clear DTCs

(f) Clear the DTCs stored in the airbag sensor assembly.

Body Electrical > SRS Airbag > Clear DTCs

(g) Turn the ignition switch off.

(h) Turn the ignition switch to ON, and wait for at least 10 seconds.

(i) Check for DTCs.

Body Electrical > Occupant Detection > Trouble Codes

OK:

DTC B1780 is not output.

HINT:

Codes other than DTC B1780 may be output at this time, but they are not related to this check.

(j) Turn the ignition switch off.

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

(l) Restore the occupant detection ECU that was installed for testing to its original location.

Click here

GO TO STEP 7

5.	REPLACE OCCUPANT DETECTION ECU

(a) Turn the ignition switch off.

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

Click here

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

6.	PERFORM ZERO POINT CALIBRATION

(a) Using the Techstream, perform Zero Point Calibration.

Click here

END

7.	REPLACE SEPARATE TYPE FRONT SEAT CUSHION SPRING ASSEMBLY RH

(a) Turn the ignition switch off.

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

Click here

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

GO TO STEP 6