Toyota CH-R Service Manual: Short in Rear Pretensioner Squib LH Circuit (B1925/78-B1928/78)

DESCRIPTION

The rear pretensioner squib LH circuit consists of the airbag sensor assembly and rear seat 3 point type outer belt assembly LH.

The airbag sensor assembly uses this circuit to deploy the pretensioner when deployment conditions are met.

These DTCs are stored when a malfunction is detected in the rear pretensioner squib LH circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Test Mode / Check Mode
B1925/78	Short in Rear Pretensioner Squib LH Circuit	Any of the following conditions is met: The airbag sensor assembly detects a line short in the rear pretensioner squib LH circuit during the primary check. Rear pretensioner squib LH malfunction Airbag sensor assembly malfunction	Floor wire Rear pretensioner squib LH (Rear seat 3 point type outer belt assembly LH) Airbag sensor assembly	Applies to check mode
B1926/78	Open in Rear Pretensioner Squib LH Circuit	Any of the following conditions is met: The airbag sensor assembly detects an open in the rear pretensioner squib LH circuit. Rear pretensioner squib LH malfunction Airbag sensor assembly malfunction	Floor wire Rear pretensioner squib LH (Rear seat 3 point type outer belt assembly LH) Airbag sensor assembly	Applies to check mode
B1927/78	Short to GND in Rear Pretensioner Squib LH Circuit	Any of the following conditions is met: The airbag sensor assembly detects a short to ground in the rear pretensioner squib LH circuit. Rear pretensioner squib LH malfunction Airbag sensor assembly malfunction	Floor wire Rear pretensioner squib LH (Rear seat 3 point type outer belt assembly LH) Airbag sensor assembly	Applies to check mode
B1928/78	Short to B+ in Rear Pretensioner Squib LH Circuit	Any of the following conditions is met: The airbag sensor assembly detects a short to B+ in the rear pretensioner squib LH circuit. Rear pretensioner squib LH malfunction Airbag sensor assembly malfunction	Floor wire Rear pretensioner squib LH (Rear seat 3 point type outer belt assembly LH) Airbag sensor assembly	Applies to check mode

DTC Detection Conditions (B1925/78):

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3
Diagnosis Condition	Ignition switch ON	○	○	○
Malfunction Status	The airbag sensor assembly detects a line short in the rear pretensioner squib LH circuit during the primary check	○	-	-
	Rear pretensioner squib LH malfunction	-	○	-
	Airbag sensor assembly malfunction	-	-	○
Detection Time		-	-	-
Number of Trips		1 trip	1 trip	1 trip

DTC Detection Conditions (B1926/78):

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3
Diagnosis Condition	Ignition switch ON	○	○	○
Malfunction Status	The airbag sensor assembly detects an open in the rear pretensioner squib LH circuit	○	-	-
	Rear pretensioner squib LH malfunction	-	○	-
	Airbag sensor assembly malfunction	-	-	○
Detection Time		-	-	-
Number of Trips		1 trip	1 trip	1 trip

DTC Detection Conditions (B1927/78):

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3
Diagnosis Condition	Ignition switch ON	○	○	○
Malfunction Status	The airbag sensor assembly detects a short to ground in the rear pretensioner squib LH circuit	○	-	-
	Rear pretensioner squib LH malfunction	-	○	-
	Airbag sensor assembly malfunction	-	-	○
Detection Time		-	-	-
Number of Trips		1 trip	1 trip	1 trip

DTC Detection Conditions (B1928/78):

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3
Diagnosis Condition	Ignition switch ON	○	○	○
Malfunction Status	The airbag sensor assembly detects a short to B+ in the rear pretensioner squib LH circuit	○	-	-
	Rear pretensioner squib LH malfunction	-	○	-
	Airbag sensor assembly malfunction	-	-	○
Detection Time		-	-	-
Number of Trips		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.

*1 Rear Seat 3 Point Type Outer Belt Assembly LH *2 Airbag Sensor Assembly *3 Floor Wire

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

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check that the connectors are properly connected to the rear seat 3 point type outer belt assembly LH and airbag sensor assembly.

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 rear seat 3 point type outer belt assembly LH and airbag sensor assembly.

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

OK:

The terminals are not deformed or damaged.

(f) Check that the floor wire connector (on the rear seat 3 point type outer belt assembly LH side) is not loose, deformed or damaged.

OK:

The connector locking button is not disengaged, and the claw of the lock is not deformed or damaged.

(g) Check that the short springs of the activation prevention mechanism of the floor wire connector are not deformed or damaged.

OK:

The short springs are not deformed or damaged.

NG

REPLACE FLOOR WIRE

OK

2.	CHECK REAR SEAT 3 POINT TYPE OUTER BELT ASSEMBLY LH

(a) Connect the connector to the airbag sensor assembly.

*1 Rear Seat 3 Point Type Outer Belt Assembly LH *2 Airbag Sensor Assembly *a Front view of wire harness connector (to Rear Seat 3 Point Type Outer Belt Assembly LH)

(b) Connect SST (resistance 2.1 Ω) to connector C.

CAUTION:

Never connect a tester to the rear seat 3 point type outer belt assembly LH for measurement, as this may lead to a serious injury due to pretensioner deployment.

SST: 09843-18061

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

(d) Clear the DTCs stored in memory.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the ignition switch off.

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

(g) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

OK:

DTC B1925/78, B1926/78, B1927/78 or B1928/78 is not output.

HINT:

Codes other than DTCs B1925/78, B1926/78, B1927/78 and B1928/78 may be output at this time, but they are not related to this check.

(h) Turn the ignition switch off.

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

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(j) Disconnect SST from connector C.

OK

REPLACE REAR SEAT 3 POINT TYPE OUTER BELT ASSEMBLY LH

NG

3.	CHECK FLOOR WIRE

(a) Disconnect the floor wire from the airbag sensor assembly.

*1 Rear Seat 3 Point Type Outer Belt Assembly LH *2 Airbag Sensor Assembly *3 Floor Wire *a Front view of wire harness connector (to Rear Seat 3 Point Type Outer Belt Assembly LH)

(b) Check for a short to B+ in the circuit.

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

(2) Turn the ignition switch ON.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
M46-1 (RL+) - Body ground	Ignition switch ON	Below 1 V
M46-2 (RL-) - Body ground	Ignition switch ON	Below 1 V

(4) Turn the ignition switch off.

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

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check for an open in the circuit.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M46-1 (RL+) - M46-2 (RL-)	Always	Below 1 Ω

(d) Check for a short to ground in the circuit.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M46-1 (RL+) - Body ground	Always	1 MΩ or higher
M46-2 (RL-) - Body ground	Always	1 MΩ or higher

(e) Check for a short in the circuit.

(1) Release the activation prevention mechanism built into connector B.

Click here

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M46-1 (RL+) - M46-2 (RL-)	Always	1 MΩ or higher

(3) Restore the released activation prevention mechanism of connector B to the original condition.

NG

REPLACE FLOOR WIRE

OK

4.

CHECK DTC

(a) Connect the connectors to the rear seat 3 point type outer belt assembly LH and airbag sensor assembly.

*1 Rear Seat 3 Point Type Outer Belt Assembly LH *2 Airbag Sensor Assembly

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

(c) Clear the DTCs stored in memory.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(d) Turn the ignition switch off.

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

(f) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

OK:

DTC B1925/78, B1926/78, B1927/78 or B1928/78 is not output.

HINT:

Codes other than DTCs B1925/78, B1926/78, B1927/78 and B1928/78 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE AIRBAG SENSOR ASSEMBLY