SUPPLEMENTAL RESTRAINT SYSTEM: OCCUPANT CLASSIFICATION SYSTEM: B1773,B1776; Belt Tension Sensor Circuit Malfunction; 2006 MY LX470 [01/2006

Last Modified: 4-30-2014	6.6 C	Doc ID: RM000001PK5001X
Model Year: 2006	Model: LX470	Prod Date Range: [01/2006 - ]
Title: SUPPLEMENTAL RESTRAINT SYSTEM: OCCUPANT CLASSIFICATION SYSTEM: B1773,B1776; Belt Tension Sensor Circuit Malfunction; 2006 MY LX470 [01/2006 - ]

DTC

B1773

Belt Tension Sensor Circuit Malfunction

DTC

B1776

Seat Belt Tension Sensor Power Source Circuit Malfunction

DESCRIPTION

The belt tension sensor circuit consists of the occupant classification ECU and the belt tension sensor.

The belt tension sensor sends the belt tension signal to the occupant classification ECU to control the occupant classification system.

DTCs B1773 and B1776 are recorded when a malfunction is detected in the belt tension sensor circuit.

DTC No.

DTC Detection Condition

Trouble Area

B1773

B1776

When one of following conditions is met:

Occupant classification ECU receives line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in belt tension sensor circuit for 2 seconds.
Belt tension sensor malfunction
Occupant classification ECU malfunction

No. 1 seat wire
Front seat outer belt RH (Belt tension sensor)
Occupant classification ECU

NOTICE:

Replace the occupant classification ECU, occupant classification sensor, seat cushion cover pad, seat cushion cover and seat cushion seat heater as a 5 part set (see supply set part no.).

HINT:

When DTC B1650/32 is detected as a result of troubleshooting the supplemental restraint system, check the DTCs stored in the occupant classification ECU, and perform troubleshooting for those DTCs first.
Use the intelligent tester to check for DTCs of the occupant classification ECU, otherwise the DTC cannot be read.

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

If troubleshooting (wire harness inspection) is difficult to perform, remove the passenger seat installation bolts to see the undersurface of the seat cushion.
In the above case, hold the seat so that it does not tip over. Holding the seat up for a long period of time may cause problems, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE

1.	CHECK FOR DTC

(a) Turn the ignition switch ON.

(b) Clear the DTCs stored in the memory .

HINT:

First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.

(d) Turn the ignition switch ON.

(e) Check the DTCs .

OK:

DTC B1773 and B1776 are not output.

HINT:

DTCs other than B1773 and B1776 may be output at this time, but they are not related to this check.

USE SIMULATION METHOD TO CHECK

2.	CHECK CONNECTOR

(a) Turn the ignition switch OFF.

(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

OK:

The connectors are properly connected.

(d) Disconnect the connectors from the occupant classification ECU and the belt tension sensor.

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

OK:

The terminals are not deformed or damaged.

HINT:

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

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK NO. 1 SEAT WIRE (TO B+)

(a) Disconnect the connectors from the occupant classification ECU and belt tension sensor.

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

(d) Measure the voltage of the wire harness side connector.

Standard voltage:

Tester Connection	Specified Condition
O5-8 (GBT) - Body ground	Below 1 V
O5-16 (BT) - Body ground	Below 1 V
O5-17 (VBT) - Body ground	Below 1 V

REPAIR OR REPLACE NO. 1 SEAT WIRE

4.	CHECK NO. 1 SEAT WIRE (FOR OPEN)

(a) Turn the ignition switch OFF.

(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

(c) Using service wire, connect terminals S38-1 (BT) and S38-3 (GBT), and connect terminals S38-2 (VBT) and S38-3 (GBT) of connector C.

NOTICE:

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

(d) Measure the resistance of the wire harness side connector.

Standard resistance:

Tester Connection	Specified Condition
O5-16 (BT) - O5-8 (GBT)	Below 1 Ω
O5-17 (VBT) - O5-8 (GBT)	Below 1 Ω

REPAIR OR REPLACE NO. 1 SEAT WIRE

5.	CHECK NO. 1 SEAT WIRE (TO GROUND)

(a) Disconnect the service wire from connector C.

(b) Measure the resistance of the wire harness side connector.

Standard resistance:

Tester Connection	Specified Condition
O5-8 (GBT) - Body ground	1 MΩ or higher
O5-16 (BT) - Body ground	1 MΩ or higher
O5-17 (VBT) - Body ground	1 MΩ or higher

REPAIR OR REPLACE NO. 1 SEAT WIRE

6.	CHECK NO. 1 SEAT WIRE (FOR SHORT)

(a) Measure the resistance of the wire harness side connector.

Standard resistance:

Tester Connection	Specified Condition
O5-16 (BT) - O5-8 (GBT)	1 MΩ or higher
O5-17 (VBT) - O5-8 (GBT)	1 MΩ or higher
O5-16 (BT) - O5-17 (VBT)	1 MΩ or higher

REPAIR OR REPLACE NO. 1 SEAT WIRE

7.	CHECK FOR DTC

(a) Connect the connectors to the occupant classification ECU and the belt tension sensor.

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

(d) Clear the DTCs stored in the memory .

HINT:

First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.

(e) Turn the ignition switch OFF.

(f) Turn the ignition switch ON.

(g) Check the DTCs .

OK:

DTCs B1773 and B1776 are not output.

HINT:

DTCs other than B1773 and B1776 may be output at this time, but they are not related to this check.

USE SIMULATION METHOD TO CHECK

8.	REPLACE FRONT SEAT OUTER BELT RH (BELT TENSION SENSOR)

(a) Turn the ignition switch OFF.

(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

HINT:

Perform the inspection using parts from a normal vehicle if possible.

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

(e) Turn the ignition switch ON.

(f) Clear the DTCs stored in the memory .

HINT:

First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.

(g) Turn the ignition switch OFF.

(h) Turn the ignition switch ON.

(i) Check the DTCs .

OK:

DTCs B1773 and B1776 are not output.

HINT:

DTCs other than B1773 and B1776 may be output at this time, but they are not related to this check.

END

9.	REPLACE OCCUPANT CLASSIFICATION ECU

(a) Connect the intelligent tester (with CAN VIM) to the DLC3.

(b) Turn the ignition switch ON.

HINT:

If the ECU data cannot be stored in the intelligent tester, replace the front seat cushion (with occupant classification ECU and occupant classification sensor).

(d) Turn the ignition switch OFF.

(e) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

(f) Replace the occupant classification ECU .

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

(h) Turn the ignition switch ON.

(i) Load the data from the previous ECU stored in the tester into the newly installed ECU .

(j) Turn the ignition switch OFF.

(k) Turn the ignition switch ON.

(l) Clear the DTCs stored in the memory .

HINT:

If DTCs are not cleared at this time, past DTCs will remain.

10.	PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check .

END