Toyota 4Runner: Open in Occupant Classification ECU Battery Positive Line (B1794)

Toyota 4Runner Service Manual / Vehicle Interior / Supplemental Restraint Systems / Occupant Classification System / Open in Occupant Classification ECU Battery Positive Line (B1794)

DESCRIPTION

DTC B1794 is stored when a malfunction is detected in the occupant classification ECU.

DTC Code	DTC Detection Condition	Trouble Area
B1794	One of the following conditions is met: Occupant classification ECU circuit malfunction. Occupant classification ECU malfunction. Occupant classification ECU detects a short circuit to ground signal in the passenger side buckle switch circuit for 2 seconds.	Harness or connector Occupant classification ECU

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 classification ECU, otherwise the DTCs cannot be read.

WIRING DIAGRAM

PROCEDURE

1.	CHECK FOR DTC

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

(b) Clear the DTCs stored in memory (See page ).

HINT:

First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.

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

(e) Using the Techstream, check for DTCs of the occupant classification ECU (See page ).

OK:

DTC B1794 is not output.

HINT:

DTCs other than DTC B1794 may be output at this time, but they are not related to this check.

USE SIMULATION METHOD TO CHECK

2.	CHECK CONNECTION OF CONNECTOR

(a) Turn the ignition 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 center airbag sensor, occupant classification sensors and occupant classification ECU.

OK:

Connectors are properly connected.

CONNECT CONNECTOR

3.	CHECK CONNECTOR

(a) Disconnect the connector from the occupant classification ECU.

(b) Check that the connectors (on the occupant classification ECU side) are not damaged (See page ).

OK:

Connectors are not deformed or damaged.

REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (SOURCE VOLTAGE)

(a) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
a9-1 (+B) - Body ground	Ignition switch ON	11 to 14 V
a9-7 (IG2) - Body ground	Ignition switch ON	11 to 14 V

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
a9-3 (GND) - Body ground	Always	Below 1 Ω

Text in Illustration

*a	Front view of wire harness connector (to Occupant Classification ECU)

REPLACE HARNESS OR CONNECTOR

5.	CHECK FOR DTC

(a) Connect the connectors to the occupant classification ECU.

(b) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

(d) Clear the DTCs stored in memory (See page ).

HINT:

First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.

(e) Turn the ignition switch off, and wait for at least 10 seconds.

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

(g) Using the Techstream, check for DTCs of the occupant classification ECU (See page ).

OK:

DTC B1794 is not output.

HINT:

DTCs other than DTC B1794 may be output at this time, but they are not related to this check.

USE SIMULATION METHOD TO CHECK

6.	REPLACE OCCUPANT CLASSIFICATION ECU

(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 when possible.

7.	PERFORM ZERO POINT CALIBRATION

(a) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

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

OK:

"Zero Point Calibration is complete." is displayed.

8.	PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (See page ).

Standard range:

27 to 33 kg (59.5 to 72.8 lb)

END

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