Toyota Tacoma (2015-2018) Service Manual: Open in Occupant Classification ECU Battery Positive Line (B1794)

Toyota Tacoma (2015-2018) Service Manual / Supplemental Restraint Systems / Occupant Classification System / Open in Occupant Classification ECU Battery Positive Line (B1794)

DESCRIPTION

DTC B1794 is set when a malfunction is detected in the occupant detection ECU.

DTC No.	DTC Detections Conditions	Trouble Areas
B1794	Occupant detection ECU circuit malfunction Occupant detection ECU malfunction The occupant detection ECU receives a short circuit to ground signal in the passenger side buckle switch circuit for 2 seconds	Wire harness Occupant detection ECU

HINT:

When DTC B1650/32 is detected as a result of troubleshooting the supplemental restraint 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

PROCEDURE

CHECK DTC

(a) Turn the ignition switch to ON.

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

HINT:

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

(d) Turn the ignition switch to ON.

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

OK:

DTC B1794 is not output.

HINT:

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

USE SIMULATION METHOD TO CHECK

2.	CHECK CONNECTION OF CONNECTORS

(a) Turn the ignition switch off.

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

OK:

The connectors are properly connected.

CONNECT CONNECTORS

3.	CHECK CONNECTORS

(a) Check that the connectors (on the occupant detection ECU side) are not damaged (See page OK: ).

OK:

The connectors are not deformed or damaged.

REPAIR OR REPLACE WIRE HARNESS

4.	CHECK WIRE HARNESS (SOURCE VOLTAGE)

(a) Turn the ignition switch off.

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

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

(e) Turn the ignition switch to ON.

(f) Measure the voltage and resistance according to the value(s) in the table below.

Standard resistance:

Tester Connection	Condition	Specified Condition
O5-3 (GND) - Body ground	Always	Below 1 Ω

Standard voltage:

Tester Connection	Switch Condition	Specified Condition
O5-1 (+B) - Body ground	Ignition switch ON	11 to 14 V
O5-7 (IG) - Body ground	Ignition switch ON	11 to 14 V

REPAIR OR REPLACE WIRE HARNESS OR BATTERY

CHECK DTC

(a) Turn the ignition switch off.

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

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

(e) Turn the ignition switch to ON.

(f) Clear any DTCs stored in the memory (See page ).

HINT:

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

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

(h) Turn the ignition switch to ON.

(i) Using the Techstream, check for DTCs of the occupant detection ECU (See page OK: ).

OK:

DTC B1794 is not output.

HINT:

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

USE SIMULATION METHOD TO CHECK

6.	REPLACE OCCUPANT DETECTION ECU

(a) Turn the ignition switch off.

(b) Disconnect the negative (-) terminal cable from the battery, 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 negative (-) terminal cable to the battery.

(b) Connect the Techstream to the DLC3.

(d) Using the Techstream, perform the zero point calibration (See page OK: ).

OK:

"Zero Point Calibration is complete." is displayed on the Techstream.

8.	PERFORM SENSITIVITY CHECK

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

Standard :

27 to 33 kg (59.52 to 72.75 lb)

END

Diagnostic Trouble Code Chart

DIAGNOSTIC TROUBLE CODE CHART If a trouble code is displayed during the DTC check, check the circuit listed for the code in the table below (proceed to the page listed for that circuit). 1. Occupa ...

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