Toyota CH-R Service Manual: Passenger Side Buckle Switch Circuit Malfunction (B1771)

DESCRIPTION

The passenger side buckle switch circuit consists of the occupant detection ECU and passenger side buckle switch (front seat inner belt assembly RH).

DTC B1771 is stored when a malfunction is detected in the passenger side buckle switch circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B1771	Passenger Side Buckle Switch Circuit Malfunction	Any of the following conditions is met: The occupant detection ECU detects a line short in the passenger side buckle switch circuit. The occupant detection ECU detects a line short to ground in the passenger side buckle switch circuit. The occupant detection ECU detects a line short to B+ in the passenger side buckle switch circuit. The occupant detection ECU detects an line open in the passenger side buckle switch circuit. Passenger side buckle switch malfunction Occupant detection ECU malfunction	Front seat wire RH Passenger side buckle switch (Front seat inner belt assembly RH) Occupant detection ECU

DTC Detection Conditions

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3	Pattern 4	Pattern 5	Pattern 6
Diagnosis Condition	Ignition switch ON	○	○	○	○	○	○
Malfunction Status	The occupant detection ECU detects a line short in the passenger side buckle switch circuit.	○	-	-	-	-	-
	The occupant detection ECU detects a line short to ground in the passenger side buckle switch circuit.	-	○	-	-	-	-
	The occupant detection ECU detects a line short to B+ in the passenger side buckle switch circuit.	-	-	○	-	-	-
	The occupant detection ECU detects an line open in the passenger side buckle switch circuit.	-	-	-	○	-	-
	Passenger side buckle switch malfunction	-	-	-	-	○	-
	Occupant detection ECU malfunction	-	-	-	-	-	○
Detection Time		-	-	-	-	-	-
Number of Trips		1 trip	1 trip	1 trip	1 trip	1 trip	1 trip

HINT:

DTC will be output when conditions for either of the patterns in the table above are met.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

Click here

PROCEDURE

1.	CHECK CONNECTORS

(a) Turn the ignition switch off.

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

(c) Check that the connectors are properly connected to the occupant detection ECU and front seat inner belt assembly RH.

OK:

The connectors are properly connected.

HINT:

If the connectors are not properly connected, reconnect the connectors and proceed to the next inspection.

(d) Disconnect the connectors from the occupant detection ECU and front seat inner belt assembly RH.

(e) Check that the terminals of the connectors are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPLACE FRONT SEAT WIRE RH

OK

2.	CHECK FRONT SEAT WIRE RH (SHORT TO B+)

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

*1 Front Seat Inner Belt Assembly RH *2 Occupant Detection ECU *3 Front Seat Wire RH *a Front view of wire harness connector (to Occupant Detection ECU)

(b) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
Y6-7 (BSW) - Body ground	Ignition switch ON	Below 1 V
Y6-9 (BGND) - Body ground	Ignition switch ON	Below 1 V

(d) Turn the ignition switch off.

(e) Disconnect the cable from the negative (-) battery terminal.

NG

REPLACE FRONT SEAT WIRE RH

OK

3.	CHECK FRONT SEAT WIRE RH (OPEN)

(a) Using a service wire, connect terminals 1 (+) and 2 (-) of connector C. NOTICE: Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

*1 Front Seat Inner Belt Assembly RH *2 Occupant Detection ECU *3 Front Seat Wire RH *4 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)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
Y6-7 (BSW) - Y6-9 (BGND)	Always	Below 1 Ω

(c) Disconnect the service wire from connector C.

NG

REPLACE FRONT SEAT WIRE RH

OK

4.	CHECK FRONT SEAT WIRE RH (SHORT)

(a) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition Y6-7 (BSW) - Y6-9 (BGND) Always 1 MΩ or higher

*1 Front Seat Inner Belt Assembly RH *2 Occupant Detection ECU *3 Front Seat Wire RH *a Front view of wire harness connector (to Occupant Detection ECU)

NG

REPLACE FRONT SEAT WIRE RH

OK

5.	CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

(a) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition Y6-7 (BSW) - Body ground Always 1 MΩ or higher Y6-9 (BGND) - Body ground Always 1 MΩ or higher

*1 Front Seat Inner Belt Assembly RH *2 Occupant Detection ECU *3 Front Seat Wire RH *a Front view of wire harness connector (to Occupant Detection ECU)

NG

REPLACE FRONT SEAT WIRE RH

OK

6.

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 (-) battery terminal.

(c) Clear the DTCs stored in the occupant detection ECU.

Click here

Body Electrical > Occupant Detection > Clear DTCs

(d) Clear the DTCs stored in the airbag sensor assembly.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON, and wait for at least 10 seconds.

(g) Check for DTCs.

Click here

Body Electrical > Occupant Detection > Trouble Codes

OK:

DTC B1771 is not output.

HINT:

Codes other than DTC B1771 may be output at this time, but they are not related to this check.

(h) Turn the ignition switch off.

OK

USE SIMULATION METHOD TO CHECK

NG

7.	CHECK FRONT SEAT INNER BELT ASSEMBLY RH

(a) Disconnect the cable from the negative (-) battery terminal.

(b) Replace the front seat inner belt assembly RH with a known good one.

Click here

HINT:

Perform the following inspection using known good parts from another vehicle if possible.

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

(d) Clear the DTCs stored in the occupant detection ECU.

Click here

Body Electrical > Occupant Detection > Clear DTCs

(e) Clear the DTCs stored in the airbag sensor assembly.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(f) Turn the ignition switch off.

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

(h) Check for DTCs.

Click here

Body Electrical > Occupant Detection > Trouble Codes

OK:

DTC B1771 is not output.

HINT:

Codes other than DTC B1771 may be output at this time, but they are not related to this check.

(i) Turn the ignition switch off.

(j) Disconnect the cable from the negative (-) battery terminal.

(k) Restore the front seat inner belt assembly RH that was installed for testing to its original location.

Click here

OK

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH

NG

8.	REPLACE OCCUPANT DETECTION ECU

(a) Turn the ignition switch off.

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

(c) Replace the occupant detection ECU with a new one.

Click here

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

NEXT

9.	PERFORM ZERO POINT CALIBRATION

(a) Using the Techstream, perform Zero Point Calibration.

Click here

Body Electrical > Occupant Detection > Utility

Tester Display
Zero Point Calibration

NEXT

END