- The occupant classification ECU receives a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in the seat belt tension sensor circuit for 2 seconds.
- A seat belt tension sensor malfunction.
- An occupant classification ECU malfunction.
| Last Modified: 11-27-2007 | 1.6 C | |
| Service Category: Vehicle Interior | Section: Supplemental Restraint Systems | |
| Model Year: 2008 | Model: LX570 | Doc ID: RM000001PK500WX |
| Title: SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM: DESCRIPTION (2008 LX570) | ||
|
DTC |
B1773 |
Belt Tension Sensor Circuit Malfunction |
|
DTC |
B1776 |
Seat Belt Tension Sensor Power Source Circuit Malfunction |
DESCRIPTION
The seat belt tension sensor circuit consists of the occupant classification ECU and the seat belt tension sensor.
The seat belt tension sensor sends the seat belt tension signal to the occupant classification ECU.
DTC B1773 and B1776 are stored when a malfunction is detected in the seat belt tension sensor circuit.
|
DTC Code |
DTC Detection Condition |
Trouble Area |
|---|---|---|
|
B1773 B1776 |
When one of the following conditions is met: |
|
HINT:
When DTC B1650 is stored as a result of troubleshooting for the "Airbag System", check the DTCs stored in the occupant classification ECU. When DTC B1773 and B1776 are output, perform troubleshooting for those DTCs first.
WIRING DIAGRAM
INSPECTION PROCEDURE
NOTICE:
-
w/ Navigation system:
After the engine switch is turned off, the HDD navigation system requires approximately 6 minutes to record various types of memory and settings. As a result, after turning the engine switch off, wait 6 minutes or more before disconnecting the cable from the negative (-) battery terminal.
-
When disconnecting the cable from the negative (-) battery terminal while performing repairs, some systems need to be initialized after the cable is reconnected
.
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 fall down.
PROCEDURE
|
1. |
CHECK FOR DTC |
(a) Turn the engine switch on (IG).
(b) Clear the DTCs stored in the occupant classification ECU
.
(c) Clear the DTCs stored in the center airbag sensor
.
(d) Turn the engine switch off.
(e) Turn the engine switch on (IG).
(f) Check for DTCs
.
OK:
DTC B1773 and B1776 are not output.
HINT:
Codes other than DTC B1773 and B1776 may be output at this time, but they are not related to this check.
|
|
2. |
CHECK CONNECTION OF CONNECTOR |
(a) Turn the engine switch off.
(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(c) Check that the connectors are properly connected to the occupant classification ECU and the seat belt tension sensor.
OK:
Connectors are properly connected.
|
|
3. |
CHECK CONNECTOR |
(a) Disconnect the connectors from the occupant classification ECU and the belt tension sensor.
(b) Check that the connectors (on the center airbag sensor side and seat belt tension sensor side) are not damaged.
OK:
Connectors are not deformed or damaged.
HINT:
If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.
|
|
4. |
CHECK SEAT BELT TENSION SENSOR CIRCUIT |
(a) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(b) Turn the engine switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
|
Tester Connection |
Switch Condition |
Specified Condition |
|---|---|---|
|
c8-8 (GBT) - Body ground |
Engine switch on (IG) |
Below 1 V |
|
c8-16 (BT) - Body ground |
||
|
c8-17 (VBT) - Body ground |
(d) Turn the engine switch off.
(e) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(f) Using 2 service wires, connect terminals 1 (GBT) and 3 (BT), and connect terminals 1 (GBT) and 2 (VBT) of connector E.
NOTICE:
Do not forcibly insert the service wire into the terminals of the connector when connecting a service wire.
(g) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
c8-16 (BT) - c8-8 (GBT) |
Always |
Below 1 Ω |
|
c8-17 (VBT) - c8-8 (GBT) |
(h) Disconnect the service wires from connector E.
(i) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
c8-8 (GBT) - Body ground |
Always |
1 MΩ or higher |
|
c8-16 (BT) - Body ground |
||
|
c8-17 (VBT) - Body ground |
||
|
c8-16 (BT) - c8-8 (GBT) |
||
|
c8-17 (VBT) - c8-8 (GBT) |
|
|
5. |
CHECK FOR DTC |
(a) Connect the connectors to the occupant classification ECU and the seat belt tension sensor.
(b) Connect the cable to the negative (-) battery terminal.
(c) Turn the engine switch on (IG).
(d) Clear the DTCs stored in the occupant classification ECU
.
(e) Clear the DTCs stored in the center airbag sensor
.
(f) Turn the engine switch off.
(g) Turn the engine switch on (IG).
(h) Check for DTCs
.
OK:
DTC B1773 and B1776 are not output.
HINT:
Codes other than DTC B1773 and B1776 may be output at this time, but they are not related to this check.
|
|
6. |
REPLACE FRONT SEAT OUTER BELT ASSEMBLY RH (SEAT BELT TENSION SENSOR) |
(a) Turn the engine switch off.
(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(c) Replace the front seat outer belt
.
HINT:
Perform the inspection using parts from a normal vehicle if possible.
(d) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(e) Turn the engine switch on (IG).
(f) Clear the DTCs stored in the occupant classification ECU
.
(g) Clear the DTCs stored in the center airbag sensor
.
(h) Turn the engine switch off.
(i) Turn the engine switch on (IG).
(j) Check for DTCs
.
OK:
DTC B1773 and B1776 are not output.
HINT:
Codes other than DTC B1773 and B1776 may be output at this time, but they are not related to this check.
|
|
7. |
REPLACE NO. 1 SEAT CUSHION ASSEMBLY (OCCUPANT CLASSIFICATION ECU) |
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Using the Techstream, save the ECU data from the ECU which is installed in the vehicle
.
(d) Turn the engine switch off.
(e) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(f) Replace the No. 1 seat cushion (occupant classification ECU)
.
(g) Connect the cable to the negative (-) battery terminal.
(h) Turn the engine switch on (IG).
(i) Using the Techstream, load the previous ECU data stored in the Techstream into the new ECU
.
(j) Turn the engine switch off.
(k) Turn the engine switch on (IG).
(l) Clear the DTCs stored in the memory
.
HINT:
If DTCs are not cleared at this time, past DTCs will remain.
|
|
8. |
PERFORM ZERO POINT CALIBRATION |
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Using the Techstream, perform zero point calibration
.
(d) Turn the engine switch off.
(e) Turn the engine switch on (IG).
(f) Clear the DTCs stored in the occupant classification ECU
.
HINT:
If the DTCs are not cleared at this time, past DTCs will remain.
|
|
9. |
PERFORM SENSITIVITY CHECK |
(a) Perform the sensitivity check
.
|
|
14. |
CHECK FRONT SEAT WIRE RH (OCCUPANT CLASSIFICATION ECU - NO. 2 FLOOR WIRE) |
(a) Turn the engine switch off.
(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(c) Disconnect the front seat wire RH connector from the No. 2 floor wire.
(d) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(e) Turn the engine switch on (IG).
(f) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
|
Tester Connection |
Switch Condition |
Specified Condition |
|---|---|---|
|
Lc2-2 (VBT) - Body ground |
Engine switch on (IG) |
Below 1 V |
|
Lc2-3 (BT) - Body ground |
||
|
Lc2-4 (GBT) - Body ground |
(g) Turn the engine switch off.
(h) Disconnect the cable from the negative (-) battery terminal, and wait for at least 2 seconds.
(i) Disconnect the front seat wire RH connector from the No. 2 floor wire.
(j) Using 2 service wires, connect terminals 8 (GBT) and 16 (BT), and connect terminals 17 (VBT) of connector B.
NOTICE:
Do not forcibly insert the service wire into the terminals of the connector when connecting a service wire.
(k) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
Lc2-4 (GBT) - Lc2-3 (BT) |
Always |
Below 1 Ω |
|
Lc2-4 (GBT) - Lc2-2 (VBT) |
(l) Disconnect the service wires from connector B.
(m) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
Lc2-4 (GBT) - Lc2-3 (BT) |
Always |
1 MΩ or higher |
|
Lc2-4 (GBT) - Lc2-2 (VBT) |
||
|
Lc2-2 (VBT) - Body ground |
||
|
Lc2-3 (BT) - Body ground |
||
|
Lc2-4 (GBT) - Body ground |
|
|
|