Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Short in Rear Side Squib LH Circuit (B1855-B1858)

DESCRIPTION

The rear side squib LH circuit consists of the airbag ECU assembly and rear seat airbag assembly LH.

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

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

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After turning the engine 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.

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HINT:

• Perform the simulation method by selecting check mode (Signal Check) using the Techstream.

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• After selecting check mode (Signal Check), perform the simulation method by wiggling each connector of the airbag system or driving the vehicle on a city road or rough road.

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PROCEDURE

(a) Turn the engine switch off.

*1 Rear Seat Airbag Assembly LH *2 Airbag ECU 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 airbag assembly LH and airbag ECU 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 airbag assembly LH and airbag ECU 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 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

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

*1 Rear Seat Airbag Assembly LH *2 Airbag ECU Assembly *a Front view of wire harness connector (to Rear Seat Airbag Assembly LH)

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

CAUTION:

Never connect a tester to the rear seat airbag assembly LH for measurement, as this may lead to a serious injury due to airbag deployment.

NOTICE:

• Do not forcibly insert SST into the terminals of the connector when connecting it.
• Insert SST straight into the terminals of the connector.

SST: 09843-18061

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

(d) Turn the engine switch on (IG), and wait for at least 60 seconds.

(e) Clear the DTCs stored in memory.

(f) Turn the engine switch off.

(g) Turn the engine switch on (IG), and wait for at least 60 seconds.

(h) Check for DTCs.

OK:

DTC B1855, B1856, B1857 or B1858 is not output.

HINT:

Codes other than DTCs B1855, B1856, B1857 and B1858 may be output at this time, but they are not related to this check.

(i) Turn the engine switch off.

(j) 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.

(k) Disconnect SST from connector C.

OK

REPLACE REAR SEAT AIRBAG ASSEMBLY LH

NG

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

*1 Rear Seat Airbag Assembly LH *2 Airbag ECU Assembly *3 Floor Wire *a Front view of wire harness connector (to Rear Seat Airbag Assembly LH)

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

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

(2) Turn the engine switch on (IG).

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

Standard Voltage:

(4) Turn the engine 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:

(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:

(e) Check for a short in the circuit.

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

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

Standard Resistance:

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

NG

REPLACE FLOOR WIRE

OK

(a) Connect the connectors to the rear seat airbag assembly LH and airbag ECU assembly.

*1 Rear Seat Airbag Assembly LH *2 Airbag ECU Assembly

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

(c) Turn the engine switch on (IG), and wait for at least 60 seconds.

(d) Clear the DTCs stored in memory.

(e) Turn the engine switch off.

(f) Turn the engine switch on (IG), and wait for at least 60 seconds.

(g) Check for DTCs.

OK:

DTC B1855, B1856, B1857 or B1858 is not output.

HINT:

Codes other than DTCs B1855, B1856, B1857 and B1858 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE AIRBAG ECU ASSEMBLY