Lexus NX: Open in Occupant Classification ECU Battery Positive Line (B1794)
DESCRIPTION
DTC B1794 is stored when a malfunction is detected in the occupant detection ECU.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area |
|---|---|---|---|
| B1794 | Open in Occupant Classification ECU Battery Positive Line | 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 B1794 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:
-
When disconnecting the cable, some systems need to be initialized after the cable is reconnected.
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- Inspect the fuses for circuits related to this system before performing the following inspection procedure.
- If troubleshooting (wire harness inspection) is difficult to perform, remove the frontseat RH installation bolts to see the undersurface of the seat cushion.
PROCEDURE
| 1. | CHECK DTC |
(a) Turn the power switch on (IG), and wait for at least 60 seconds.
(b) Clear the DTCs.
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HINT:
- First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.
- Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.
(c) Turn the power switch off.
(d) Turn the power switch on (IG), and wait for at least 60 seconds.
(e) Check for DTCs.
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HINT:
DTCs other than DTC B1794 may be output at this time, but they are not related to this check.
| DTC B1794 is not output | .gif) | USE SIMULATION METHOD TO CHECK |
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| 2. | CHECK CONNECTION OF CONNECTOR |
(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 connector is properly connected to the occupant detection ECU.
| Connector is not properly connected | | CONNECT CONNECTOR |
|
| 3. | CHECK CONNECTOR |
(a) Disconnect the connector from the occupant detection ECU.
(b) Check that the connector (on the occupant detection ECU side) are not damaged.
| Connectors are deformed or damaged | | REPLACE HARNESS OR CONNECTOR |
|
| 4. | CHECK HARNESS AND CONNECTOR (OCCUPANT DETECTION ECU - BATTERY AND BODY GROUND) |
| (a) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds. |
|
(b) Turn the power switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Switch Condition | Specified Condition |
|---|---|---|
| f15-1 (+B) - Body ground | Power switch off | 11 to 14 V |
| f15-6 (IG2) - Body ground | Power switch on (IG) |
(d) Turn the power switch off.
(e) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.
(f) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| f15-3 (GND) - Body ground | Always | Below 1 Ω |
| NG | | REPLACE HARNESS OR CONNECTOR |
|
| 5. | CHECK DTC |
(a) Connect the connector to the occupant detection ECU.
(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.
- Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.
(e) Turn the power switch off.
(f) Turn the power switch on (IG), and wait for at least 60 seconds.
(g) Check for DTCs.
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HINT:
DTCs other than DTC B1794 may be output at this time, but they are not related to this check.
| DTC B1794 is not output | | USE SIMULATION METHOD TO CHECK |
|
| 6. | 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.
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HINT:
Perform the inspection using parts from a normal vehicle when possible.
|
| 7. | PERFORM ZERO POINT CALIBRATION |
(a) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.
(b) Turn the power switch on (IG).
(c) Perform the zero point calibration.
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|
| 8. | PERFORM SENSITIVITY CHECK |
(a) Perform the sensitivity check.
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Standard:
27 to 33 kg (59.5 to 72.8 lb)
| NEXT | | END (OCCUPANT DETECTION ECU WAS DEFECTIVE) |
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