Lexus NX: Passenger Side Buckle Switch Circuit Malfunction (B1771)
DESCRIPTION
The front passenger side buckle switch circuit consists of the occupant detection ECU and front seat inner belt assembly RH.
DTC B1771 is stored when a malfunction is detected in the front passenger side buckle switch circuit.
Troubleshoot DTC B1771 first when DTCs B1771 and B1795 are output simultaneously.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area |
|---|---|---|---|
| B1771 | Passenger Side Buckle Switch Circuit Malfunction | One of the following conditions is met:
|
|
HINT:
- When DTC B1650/32 is stored as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1771 of the occupant classification system.
- Use the Techstream to check for DTCs of the occupant detection ECU, otherwise the DTCs cannot be read.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
-
After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal.
Click here
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-
When disconnecting and reconnecting the auxiliary battery
Click here
HINT:
When disconnecting and reconnecting the battery, there is an automatic learning function that completes learning when the respective system is used.
Click here
HINT:
- If troubleshooting (wire harness inspection) is difficult to perform, remove the front seat RH installation bolts to see the undersurface of the seat cushion.
- In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat up only for as long as necessary.
PROCEDURE
| 1. | CHECK DTC |
(a) Turn the power switch on (IG), and wait for at least 60 seconds.
(b) Clear the DTCs.
Click here
HINT:
First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.
(c) Turn the power switch off.
(d) Turn the power switch on (IG), and wait for at least 60 seconds.
(e) Check for DTCs.
Click here
HINT:
Codes other than DTC B1771 may be output at this time, but they are not related to this check.
| DTC B1771 is not output | .gif) | USE SIMULATION METHOD TO CHECK |
|
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| 2. | CHECK CONNECTION OF CONNECTORS |
(a) Turn the power switch off.
(b) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.
(c) Check that the connectors are properly connected to the occupant detection ECU and front seat inner belt.
| Connectors are not properly connected | | CONNECT CONNECTORS |
|
| 3. | CHECK CONNECTORS |
| (a) Disconnect the connectors from the occupant detection ECU and front seat inner belt assembly RH. |
|
(b) Check that the connectors (on the occupant detection ECU side and front seat inner belt assembly RH side) are not damaged.
| Connectors are deformed or damaged | | REPLACE FRONT SEAT WIRE RH |
|
| 4. | CHECK DTC |
(a) Connect the connectors to the occupant detection ECU and front seat inner belt assembly RH.
(b) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.
(c) Turn the power switch on (IG), and wait for at least 60 seconds.
(d) Clear the DTCs.
Click here
HINT:
First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.
(e) Turn the power switch off.
(f) Turn the power switch on (IG), and wait for at least 60 seconds.
(g) Check for DTCs.
Click here
HINT:
Codes other than DTC B1771 may be output at this time, but they are not related to this check.
| DTC B1771 is not output | | USE SIMULATION METHOD TO CHECK |
|
| 5. | CHECK FRONT SEAT WIRE RH |
(a) Measure the voltage according to the value(s) in the table below.
| *1 | Front Seat Inner Belt Assembly RH | *2 | Occupant Detection ECU |
| *3 | Front Seat Wire RH | *4 | Connector B |
| *5 | Connector C | *6 | Service Wire |
| *a | Front view of wire harness connector (to Occupant Detection ECU) | *b | Front view of wire harness connector (to Front Seat Inner Belt Assembly RH) |
Standard Voltage:
| Tester Connection | Switch Condition | Specified Condition |
|---|---|---|
| f15-8 (BSW) - Body ground | Power switch on (IG) | Below 1 V |
| f15-5 (BGND) - Body ground |
(b) Turn the power switch off.
(c) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.
(d) Using service wires, connect terminals 1 (+) and 2 (-) of connector C.
NOTICE:
Do not forcibly insert the service wires into the terminals of the connector.
(e) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| f15-8 (BSW) - f15-5 (BGND) | Always | Below 1 Ω |
(f) Disconnect the service wires from connector C.
(g) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| f15-8 (BSW) - f15-5 (BGND) | Always | 1 MΩ or higher |
| f15-8 (BSW) - Body ground | ||
| f15-5 (BGND) - Body ground |
| NG | | REPLACE FRONT SEAT WIRE RH |
|
| 6. | CHECK FRONT SEAT INNER BELT ASSEMBLY RH |
(a) Replace the front seat inner belt assembly RH.
Click here
HINT:
Perform the inspection using parts from a normal vehicle when possible.
(b) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.
(c) Turn the power switch on (IG), and wait for at least 60 seconds.
(d) Clear the DTCs.
Click here
HINT:
First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.
(e) Turn the power switch off.
(f) Turn the power switch on (IG), and wait for at least 60 seconds.
(g) Check for DTCs.
Click here
HINT:
Codes other than DTC B1771 may be output at this time, but they are not related to this check.
| DTC B1771 is not output | | END (FRONT SEAT INNER BELT ASSEMBLY RH WAS DEFECTIVE) |
|
| 7. | REPLACE OCCUPANT DETECTION ECU |
(a) Turn the power switch off.
(b) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.
(c) Replace the occupant detection ECU.
Click here
HINT:
Perform the inspection using parts from a normal vehicle when possible.
(d) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.
|
| 8. | PERFORM ZERO POINT CALIBRATION |
(a) Perform the zero point calibration.
Click here
|
| 9. | PERFORM SENSITIVITY CHECK |
(a) Perform the sensitivity check.
Click here
Standard:
27 to 33 kg (59.5 to 72.8 lb)
| NEXT | | END (OCCUPANT DETECTION ECU WAS DEFECTIVE) |
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*: Use the Techstream.
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